U.S. patent number 10,856,812 [Application Number 15/751,733] was granted by the patent office on 2020-12-08 for methods and apparatus for detecting motion via optomechanics.
This patent grant is currently assigned to Valencell, Inc.. The grantee listed for this patent is Valencell, Inc.. Invention is credited to Michael Edward Aumer, Lawrence Christopher Eschbach, Steven Matthew Just, Steven Francis LeBoeuf, Seth Long, Jesse Berkley Tucker, Wolfgang Wagner, Jonathan T. Walter.
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United States Patent |
10,856,812 |
Walter , et al. |
December 8, 2020 |
Methods and apparatus for detecting motion via optomechanics
Abstract
Methods and apparatus are described for facilitating the
extraction of cleaner biometric signals from biometric monitors. A
motion reference signal is generated independently from a biometric
signal and then the motion reference signal is used to remove
motion artifacts from the biometric signal.
Inventors: |
Walter; Jonathan T. (Wake
Forest, NC), Just; Steven Matthew (Cary, NC), Wagner;
Wolfgang (Chapel Hill, NC), LeBoeuf; Steven Francis
(Raleigh, NC), Tucker; Jesse Berkley (Youngsville, NC),
Aumer; Michael Edward (Raleigh, NC), Eschbach; Lawrence
Christopher (Louisburg, NC), Long; Seth (Raleigh,
NC) |
Applicant: |
Name |
City |
State |
Country |
Type |
Valencell, Inc. |
Raleigh |
NC |
US |
|
|
Assignee: |
Valencell, Inc. (Raleigh,
NC)
|
Family
ID: |
1000005227750 |
Appl.
No.: |
15/751,733 |
Filed: |
August 10, 2016 |
PCT
Filed: |
August 10, 2016 |
PCT No.: |
PCT/US2016/046273 |
371(c)(1),(2),(4) Date: |
February 09, 2018 |
PCT
Pub. No.: |
WO2017/027551 |
PCT
Pub. Date: |
February 16, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180353134 A1 |
Dec 13, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62345579 |
Jun 3, 2016 |
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62257502 |
Nov 19, 2015 |
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62204214 |
Aug 12, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
5/14551 (20130101); A61B 5/02416 (20130101); A61B
5/721 (20130101); A61B 5/6817 (20130101); A61B
5/6843 (20130101); A61B 5/7214 (20130101); A61B
5/6804 (20130101); A61B 5/14552 (20130101); A61B
2562/146 (20130101); A61B 2562/185 (20130101); A61B
5/6802 (20130101) |
Current International
Class: |
A61B
5/1455 (20060101); A61B 5/00 (20060101); A61B
5/024 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1692874 |
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Nov 2005 |
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CN |
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101803925 |
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Aug 2010 |
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CN |
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101033472 |
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May 2011 |
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KR |
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WO 2007/023426 |
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Mar 2007 |
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WO |
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WO 2007/038432 |
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Apr 2007 |
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WO |
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2012134395 |
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Oct 2012 |
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WO |
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WO 2013/132147 |
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Sep 2013 |
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WO |
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2015001434 |
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Jan 2015 |
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WO |
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2015084376 |
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Jun 2015 |
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WO |
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WO 2016/140835 |
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Sep 2016 |
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WO |
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Other References
Communication with Supplementary European Search Report, EP
Application No. 16835810.9, dated Jul. 3, 2018, 8 pp. cited by
applicant .
International Search Report, International Application No.
PCT/US2016/046273, dated Nov. 25, 2016, 5 pp. cited by applicant
.
Written Opinion of the International Searching Authority,
International Application No. PCT/US2016/046273, dated Nov. 25,
2016, 17 pp. cited by applicant .
"First Office Action and English language translation", CN
Application No. 201680047372.7, dated Jul. 9, 2020, 17 pp. cited by
applicant.
|
Primary Examiner: Fardanesh; Marjan
Attorney, Agent or Firm: Myers Bigel, P.A.
Parent Case Text
RELATED APPLICATIONS
This application is a 35 U.S.C. .sctn. 371 national stage
application of PCT Application No. PCT/US2016/046273, filed Aug.
10, 2016, which itself claims the benefit of and priority to U.S.
Provisional Patent Application No. 62/204,214 filed Aug. 12, 2015,
U.S. Provisional Patent Application No. 62/257,502 filed Nov. 19,
2015, and U.S. Provisional Patent Application No. 62/345,579 filed
Jun. 3, 2016, the disclosures of all of which are incorporated
herein by reference as if set forth in their entireties. The
above-referenced PCT International Application was published in the
English language as International Publication No. WO 2017/027551 A1
on Feb. 16, 2017.
Claims
That which is claimed is:
1. A sensor module configured to be worn by a subject, the sensor
module comprising: a housing; at least one optical emitter and at
least one optical detector supported by the housing; and a
stabilizer member movably supported by the housing, wherein the
stabilizer member comprises a portion that extends through a first
aperture in the housing and that is configured to engage a body of
the subject; wherein the at least one optical emitter is configured
to direct light through a second aperture in the housing and into
the body of the subject via a first optical pathway and to direct
light at a portion of the stabilizer member within the housing
along a second optical pathway, and wherein the at least one
optical detector is configured to detect light from the body of the
subject via a third aperture in the housing and generate a first
signal comprising subject physiological information, and wherein
the at least one optical detector is configured to detect light
scattered by the stabilizer member and generate a second signal
comprising subject motion information.
2. The sensor module of claim 1, wherein the at least one optical
emitter comprises at least one first optical emitter configured to
direct light into the body of the subject via the first optical
pathway, and at least one second optical emitter configured to
direct light at the stabilizer member along the second optical
pathway.
3. The sensor module of claim 1, wherein the first and second
optical pathways are optically isolated from each other, and/or
wherein the housing comprises substantially opaque material.
4. The sensor module of claim 1, further comprising a light guide
supported by the housing and wherein the at least one optical
emitter is configured to direct light into the body of the subject
via the light guide.
5. The sensor module of claim 4, wherein the light guide comprises
a plurality of portions that extend through respective apertures in
the housing and are configured to engage portions of the body of
the subject.
6. The sensor module of claim 1, further comprising at least one
signal processor configured to process the first and second signals
so as to remove motion artifacts from the first signal.
7. The sensor module of claim 1, wherein the sensor module is
configured to be positioned at or within an ear of the subject,
secured to an appendage of the subject, integrated within a
wearable device, and/or integrated within clothing worn by the
subject.
8. The sensor module of claim 1, further comprising a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway.
9. A method of removing motion artifacts from a biometric signal
generated by a sensor module worn by a subject, wherein the sensor
module includes a stabilizer member, at least one optical emitter,
and at least one optical detector, the method comprising: directing
light from the at least one optical emitter into a body of the
subject via a first optical pathway; directing light from the at
least one optical emitter at the stabilizer member along a second
optical pathway; detecting light from the body of the subject and
generating a first signal comprising subject physiological
information; detecting light scattered by the stabilizer member and
generating a second signal comprising subject motion information;
and processing the first and second signals so as to remove motion
artifacts from the first signal.
10. The method of claim 9, wherein the at least one optical emitter
comprises first and second optical emitters, and wherein the method
comprises directing light from the first optical emitter into the
body of the subject via the first optical pathway, and directing
light from the second optical emitter at the stabilizer member
along the second optical pathway.
11. The method of claim 9, wherein the at least one optical
detector comprises first and second optical detectors, and wherein
the method comprises detecting light from the body of the subject
and generating a first signal comprising subject physiological
information via the first optical detector, and detecting
physically modulated light scattered by the stabilizer member and
generate a second signal comprising subject motion information via
the second optical detector.
12. The method of claim 9, wherein the first and second optical
pathways are optically isolated from each other.
Description
FIELD OF THE INVENTION
io The present invention relates generally to monitoring devices
and methods and, more particularly, to monitoring devices and
methods for measuring physiological information.
BACKGROUND OF THE INVENTION
Wearable devices capable of monitoring physiological information,
such as heart rate, are increasingly being used. These devices come
in various form factors, including devices configured to be worn at
the ear or at other locations of the body, and including devices
carried or worn by a person, such as smartphones, etc. U.S. Pat.
Nos. 8,652,040, 8,700,111, 8,647,270, 8,788,002, 8,886,269, and
8,929,965, which are incorporated herein by reference in their
entireties, describe various wearable devices configured to monitor
physiological information, including headsets, earbuds, and wrist
bands.
Physiological information obtained from a subject can be used to
generate various types of health and fitness assessments of the
subject. For example, using a photoplethysmography (PPG) sensor
incorporated into a wearable monitoring device, blood flow
information can be measured during daily activities of a subject
and this information can be used to generate assessments, such as
maximum oxygen consumption VO.sub.2max, total energy expenditure
(TEE), etc.
Unfortunately, a biometric signal from a physiological sensor of a
wearable device typically includes subject motion-related noise,
and PPG sensors are particularly sensitive to motion-related noise.
Moreover, efforts to use accelerometer- or gyroscopic-based signals
as motion noise references for cleaning up PPG signals have seen
limited success, as these motion-related signals do not perfectly
represent the motion noise characteristics reflected in PPG
signals. As such, complex signal processing may be required in
order to extract pure biometric information (i.e. heart rate,
breathing rate) from motion-related noise embedded in the sensor
signal.
SUMMARY
It should be appreciated that this Summary is provided to introduce
a selection of concepts in a simplified form, the concepts being
further described below in the Detailed Description. This Summary
is not intended to identify key features or essential features of
this disclosure, nor is it intended to limit the scope of the
invention.
Embodiments of the present invention facilitate the extraction of
cleaner biometric signals from biometric monitors, such as PPG
sensors and the like, by generating a motion reference signal
independently from a biometric signal and then using this motion
reference signal to remove motion artifacts from the biometric
signal.
According to some embodiments of the present invention, a device
for sensing physiological and body motion information includes at
least one optical emitter and at least one optical detector, and at
least two optical pathways. One optical pathway is configured to
sense body motion information by sensing light from the at least
one emitter scattered by body motion. The other optical pathway is
configured to sense physiological information by sensing light from
the at least one emitter scattered from the body by blood flow.
According to some embodiments of the present invention, a biometric
sensor module includes a housing, a stabilizer member supported by
the housing, at least one optical emitter supported by the housing,
and at least one optical detector supported by the housing. The at
least one optical emitter is configured to direct light into the
body of the subject via a first optical pathway and to direct light
at the stabilizer member along a second optical pathway. The first
and second optical pathways may be optically isolated from each
other. The at least one optical detector is configured to detect
light from the body of the subject and generate a first signal
comprising subject physiological information, and is also
configured to detect light reflected by the stabilizer member and
generate a second signal comprising subject motion information. The
sensor module may include at least one signal processor configured
to process the first and second signals so as to remove motion
artifacts from the first signal.
In some embodiments, the stabilizer member may include an optical
filter that is configured to pass, block, or scatter multiple
different wavelengths of light representative of subject motion. In
other embodiments, the at least one optical emitter may be
configured to direct light into the body of the subject and/or at
the stabilizer member in multiple different wavelengths.
In some embodiments, the at least one optical emitter includes a
first optical emitter configured to direct light into the body of
the subject via the first optical pathway, and a second optical
emitter configured to direct light at the stabilizer member along
the second optical pathway. The second optical emitter may include
at least one optical element configured to direct light at the
stabilizer member, such as a lens, filter, and/or reflective
element.
In some embodiments, the at least one optical detector includes a
first optical detector configured to detect light from the body of
the subject and generate a first signal comprising subject
physiological information, and a second optical detector configured
to detect physically modulated light reflected by the stabilizer
member and generate a second signal comprising subject motion
information. The light reflected by the stabilizer member is
physically modulated due to subject motion.
In some embodiments, the stabilizer member is movably supported by
the housing and includes a portion that extends from the housing
and is configured to engage the body of the subject.
In some embodiments, the first optical pathway and/or the second
optical pathway comprises light guiding material.
In some embodiments, the housing comprises substantially opaque
material.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage or other body location of the subject, or even integrated
within clothing worn by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway at or prior to the time when the at least one optical
detector detects light from the body and generates a physiological
information signal.
According to other embodiments of the present invention, a sensor
module configured to be worn by a subject includes a housing, at
least one optical emitter supported by the housing, and at least
one optical detector supported by the housing. The at least one
optical emitter is configured to direct light into the body of the
subject via a first optical pathway and to direct light at the body
along a second pathway. The first and second optical pathways may
be optically isolated from each other. The at least one optical
detector is configured to detect light from the body of the subject
and generate a first signal comprising subject physiological
information, and wherein the at least one optical detector is
configured to detect light reflected by the body and generate a
second signal comprising subject motion information. This reflected
light may be physically modulated due to subject motion. The sensor
module may include at least one signal processor configured to
process the first and second signals so as to remove motion
artifacts from the first signal.
In some embodiments, the at least one optical emitter includes a
first optical emitter configured to direct light into the body of
the subject via the first optical pathway, and a second optical
emitter configured to direct light at the body along the second
optical pathway.
In some embodiments, the at least one optical detector includes a
first optical detector configured to detect light from the body of
the subject and generate a first signal comprising subject
physiological information, and a second optical detector configured
to detect light reflected by the body and generate a second signal
comprising subject motion information.
In some embodiments, the first optical pathway and/or the second
optical pathway comprises light guiding material.
In some embodiments, the housing comprises substantially opaque
material.
In some embodiments, the at least one optical emitter is configured
to direct light into the body of the subject and/or at the body of
the subject in multiple different wavelengths.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage or other body location of io the subject, or even
integrated within clothing worn by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway at or prior to the time when the at least one optical
detector detects light from the body and generates a physiological
information signal.
According to other embodiments of the present invention, a sensor
module configured to be worn by a subject includes a housing, at
least one optical emitter and at least one optical detector
supported by the housing, and a stabilizer member movably supported
by the housing. The stabilizer member includes a portion that
extends through a first aperture in the housing and is configured
to engage the body of the subject. The at least one optical emitter
is configured to direct light through a second aperture in the
housing and into the body of the subject via a first optical
pathway and to direct light at a portion of the stabilizer member
within the housing along a second optical pathway. The first and
second optical pathways may be optically isolated from each other.
The at least one optical detector is configured to detect light
from the body of the subject via a third aperture in the housing
and generate a first signal comprising subject physiological
information, and wherein the at least one optical detector is
configured to detect light reflected by the stabilizer member and
generate a second signal comprising subject motion information. The
sensor module may include at least one signal processor configured
to process the first and second signals so as to remove motion
artifacts from the first signal.
In some embodiments, the at least one optical emitter includes at
least one first optical emitter configured to direct light into the
body of the subject via the first optical pathway, and at least one
second optical emitter configured to direct light at the stabilizer
member along the second optical pathway.
In some embodiments, a light guide is supported by the housing and
the at least one optical emitter is configured to direct light into
the body of the subject via the light guide. The light guide may
include a plurality of portions that extend through respective
apertures in the housing and that are configured to engage portions
of the body of the subject.
In some embodiments, the housing is formed of substantially opaque
material.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage or other body location of the subject, or even integrated
within clothing worn by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway at or prior to the time when the at least one optical
detector detects light from the body and generates a physiological
information signal.
According to other embodiments of the present invention, a sensor
module configured to be worn by a subject includes a housing, first
and second optical emitters supported by the housing, an optical
detector supported by the housing, and first and second light
guides supported by the housing. The first light guide is in
optical communication with the first optical emitter and defines a
first optical pathway, and the second light guide is in optical
communication with the second optical emitter and defines a second
optical pathway. The first and second optical pathways may be
optically isolated from each other. The first optical emitter is
configured to direct light into the body of the subject via the
first optical pathway, and the second optical emitter is configured
to direct light at the body of the subject via the second optical
pathway. The optical detector is configured to detect light from
the body of the subject and generate a first signal comprising
subject physiological information. The optical detector also is
configured to detect light reflected by the body of the subject and
generate a second signal comprising subject motion information. The
light reflected by the body may be physically modulated due to
subject motion. The sensor module may include at least one signal
processor configured to process the first and second signals so as
to remove motion artifacts from the first signal.
In some embodiments, the first light guide includes a portion that
extends through an aperture in the housing and is configured to
engage the body of the subject.
In some embodiments, the housing is formed of substantially opaque
material.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage or other body location of the subject, or even integrated
within clothing worn by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway at or prior to the time when the optical detector detects
light from the body and generates a physiological information
signal.
According to other embodiments of the present invention, a sensor
module configured to be worn by a subject includes a housing, at
least one optical detector supported by the housing, at least one
optical emitter supported by the housing, and a stabilizer member
movably supported by the housing. The stabilizer member includes a
portion that extends from the housing and engages the body of the
subject. The at least one optical emitter is configured to direct
light into the body of the subject via a first optical pathway and
to direct light at the at least one optical detector along a second
optical pathway. The first and second optical pathways typically
are optically isolated from each other. The stabilizer member is
configured to modulate an amount of light in the second optical
pathway by modulating a volume of the second optical pathway.
The at least one optical detector is configured to detect light
from the body of the subject and generate a first signal containing
subject physiological information. The at least one optical
detector is configured to detect light in the second optical
pathway and generate a second signal containing subject motion
information. The sensor module may include at least one signal
processor configured to process the first and second signals so as
to remove motion artifacts from the first signal.
In some embodiments, the first optical pathway and/or the second
optical pathway includes light guiding material.
In some embodiments, the second optical pathway includes a
plurality of light channels, and the stabilizer member is
configured to modulate an amount of light in the second optical
pathway responsive to subject motion by modulating a volume of the
plurality of light channels.
In some embodiments, the housing comprises substantially opaque
material.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage or other body location of the subject, or even integrated
within clothing worn by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the first optical
pathway at or prior to the time when the at least one optical
detector detects light from the body and generates a physiological
information signal.
According to other embodiments of the present invention, a sensor
module configured to be worn by a subject includes a housing, a
pressure transducer supported by the housing, at least one optical
emitter supported by the housing, at least one optical detector
supported by the housing, and a stabilizer member movably supported
by the housing. The stabilizer member is configured to modulate the
pressure transducer responsive to subject motion and includes a
portion that extends from the housing and engages the body of the
subject. The at least one optical emitter is configured to direct
light into the body of the subject. The at least one optical
detector is configured to detect light from the body of the subject
and generate a first signal containing subject physiological
information. The pressure transducer is configured to generate a
second signal containing subject motion information. The sensor
module may include at least one signal processor configured to
process the first and second signals so as to remove motion
artifacts from the first signal.
In some embodiments, the sensor module is configured to be
positioned at or within an ear of the subject. In other
embodiments, the sensor module is configured to be secured to an
appendage of the subject, or even integrated within clothing worn
by the subject.
In some embodiments, the sensor module includes a blood flow
stimulator configured to increase blood perfusion at a location of
the body of the subject receiving light via the at least one
optical emitter at or prior to the time when the at least one
optical detector detects light from the body and generates a
physiological information signal.
According to other embodiments of the present invention, a method
of removing motion artifacts from a biometric signal generated by a
sensor module worn by a subject is provided. The sensor module
includes a stabilizer member, at least one optical emitter, and at
least one optical detector. The method includes directing light
from the at least one optical emitter into the body of the subject
via a first optical pathway, directing light from the at least one
optical emitter at the stabilizer member along a second optical
pathway, detecting light from the body of the subject and
generating a first signal comprising subject physiological
information, detecting light reflected by the stabilizer member and
generating a second signal comprising subject motion information,
and processing the first and second signals so as to remove motion
artifacts from the first signal.
In some embodiments, the at least one optical emitter includes
first and second optical emitters, and the method includes
directing light from the first optical emitter into the body of the
subject via the first optical pathway, and directing light from the
second optical emitter at the stabilizer member along the second
optical pathway.
In some embodiments, the at least one optical detector includes
first and second optical detectors, and the method includes
detecting light from the body of the subject and generating a first
signal comprising subject physiological information via the first
optical detector, and detecting physically modulated light
reflected by the stabilizer member and generate a second signal
comprising subject motion information via the second optical
detector.
In some embodiments, the first and second optical pathways are
optically isolated from each other.
According to other embodiments of the present invention, a method
of removing motion artifacts from a biometric signal generated by a
sensor module worn by a subject is provided. The sensor module
includes at least one optical emitter and at least one optical
detector and the method includes directing light from the at least
one optical emitter into the body of the subject via a first
optical pathway and at the body of the subject along a second
optical pathway, detecting light from the body of the subject and
generating a first signal containing subject physiological
information, detecting light reflected by the body of the subject
and generating a second signal containing subject motion
information, and processing the first and second signals so as to
remove motion artifacts from the first signal.
In some embodiments, the at least one optical emitter includes
first and second optical emitters, and the method includes
directing light from the first optical emitter into the body of the
subject via the first optical pathway, and directing light from the
second optical emitter at the body along the second optical
pathway.
In some embodiments, the at least one optical detector includes
first and second optical detectors, and the method includes
detecting light from the body of the subject and generating a first
signal containing subject physiological information via the first
optical detector, and detecting light reflected by the body and
generating a second signal containing subject motion information
via the second optical detector.
In some embodiments, the first and second optical pathways are
optically isolated from each other.
According to other embodiments of the present invention, a device,
such as a smartphone or other portable electronic device, includes
a sensor module configured to obtain physiological information from
a body location of a subject, and a blood flow stimulator
configured to increase blood perfusion at the body location at or
prior to the time when the sensor module obtains the physiological
information. The blood flow stimulator may include a heater, such
as an infrared (IR) heater, configured to increase blood perfusion.
In some embodiments the blood flow stimulator includes a mechanical
actuator configured to apply physical stimulation to the body
location. For example, in some embodiments, the device is a
smartphone, and the blood flow stimulator is a vibration actuator
within the smartphone configured to provide haptic feedback to a
user.
In some embodiments, the sensor module includes a stabilizer
member, at least one optical emitter, and at least one optical
detector. The at least one optical emitter is configured to direct
light into the body of the subject via a first optical pathway and
to direct light at the stabilizer member along a second optical
pathway. The at least one optical detector is configured to detect
light from the body of the subject and generate a first signal
comprising subject physiological information, and to detect light
reflected by the stabilizer member and generate a second signal
comprising subject motion information.
In some embodiments, the sensor module includes at least one
optical emitter and at least one optical detector. The at least one
optical emitter is configured to direct light into the body of the
subject via a first optical pathway and to direct light at the body
along a second pathway. The at least one optical detector is
configured to detect light from the body of the subject and
generate a first signal comprising subject physiological
information, and to detect light reflected by the body and generate
a second signal comprising subject motion information.
According to other embodiments of the present invention, a wearable
device includes an optical sensor that is configured to detect
optically derived physiological information from a location on a
body of a subject, and that includes at least one optical emitter
and at least one optical detector. The wearable device also
includes a thermal energy generator configured to raise a
temperature of the body at the location, a temperature sensor
configured to sense body temperature information at the location,
and at least one circuit configured to control electrical biasing
of the at least one optical emitter, the thermal energy generator,
and the temperature sensor. In addition, the wearable device
includes data storage configured to receive and store data from the
optical sensor and temperature sensor, and a processor that is
configured to process data in the data storage from the optical
sensor in context with data in the data storage from the
temperature sensor to generate a physiological assessment for the
subject.
In some embodiments, the at least one circuit is configured to
electrically bias the at least one optical emitter at set time
periods associated with electrical biasing of the thermal energy
generator.
In some embodiments, the at least one optical emitter includes a
plurality of optical emitters, and the at least one circuit is
configured to alternately bias the plurality of optical emitters in
time to generate a matrix of data including optical emitter
wavelength information and temperature information.
In some embodiments, the optical sensor is configured to sense
scattered light and luminescent light from the location, and
wherein the at least one circuit is configured to alternately bias
the plurality of optical emitters in time to generate a matrix of
data including optical emitter wavelength information, temperature
information, and time information.
In some embodiments, the at least one optical detector includes a
plurality of optical detectors, and at least one of the plurality
of optical detectors is configured to detect at least one
wavelength of light that at least one other of the plurality of
optical detectors is configured to not detect. Data from the
plurality of optical detectors is used to generate a matrix of data
including optical emitter wavelength information and temperature
information.
According to other embodiments of the present invention, a wearable
device includes a sensor module, such as a PPG sensor module, that
is configured to obtain physiological information from a body
location of a subject wearing the device. The wearable device also
includes a bladder of compliant material that contains a fluid,
such as a liquid, gas or gel. The bladder is configured to contact
the skin of the subject at or adjacent the body location. The
bladder may have various shapes and configurations. In some
embodiments, the bladder has a ring shape that peripherally
surrounds the sensor module.
A pressure sensor is provided that generates a signal proportional
to a change in fluid pressure within the bladder. The change in
pressure is responsive to motion of the subject. As such, the
pressure sensor generates a motion noise reference signal that can
be used to remove motion artifacts from the physiological
information obtained by the sensor module.
In some embodiments, the bladder is configured to at least
partially wrap around a limb of the subject.
In some embodiments, the bladder includes at least one fluid
reservoir containing a fluid and a plurality of artificial blood
vessels in fluid communication with the at least one fluid
reservoir. Compression of the bladder due to subject motion causes
the fluid to be forced from the at least one fluid reservoir into
the artificial vessels, thereby creating pressure within the
bladder that can be detected by the pressure sensor. Such a
configuration may be useful to more closely resemble that of venous
blood in the body, such that the artificial structure may generate
a motion noise waveform that more closely resembles that of the
subject's venous blood as it moves during motion, facilitating use
as a noise reference as described above. It should be noted that
the blood vessels and reservoir may further comprise at least one
air bubble (air pocket) to facilitate fluid flow during motion. In
some embodiments, the density of air bubbles and the viscosity of
blood may be engineered to closely resemble that of the blood of
the subject. In another embodiment, the fluid may comprise a
plurality of fluids, each having a different density and/or
polarity. Having such a distribution of fluids may more closely
resemble the nature of the venous blood of the subject.
In some embodiments, the pressure sensor is a MEMS
(micro-electromechanical systems) device, diaphragm, and/or
actuator. In other embodiments, the pressure sensor is an
optomechanical pressure sensor.
It is noted that aspects of the invention described with respect to
one embodiment may be incorporated in a different embodiment
although not specifically described relative thereto. That is, all
embodiments and/or features of any embodiment can be combined in
any way and/or combination. Applicant reserves the right to change
any originally filed claim or file any new claim accordingly,
including the right to be able to amend any originally filed claim
to depend from and/or incorporate any feature of any other claim
although not originally claimed in that manner. These and other
objects and/or aspects of the present invention are explained in
detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which form a part of the specification,
illustrate various embodiments of the present invention. The
drawings and description together serve to fully explain
embodiments of the present invention.
FIGS. 1-2 illustrate "internal" optomechanical biometric sensor
modules and motion information and biometric information pathways
generated thereby, according to some embodiments of the present
invention.
FIGS. 3-5 illustrate "external" optomechanical biometric sensor
modules and motion information and biometric information pathways
generated thereby, according to some embodiments of the present
invention.
FIG. 6 illustrates an "internal" optomechanical biometric sensor
module and motion information and biometric information pathways
generated thereby, according to some embodiments of the present
invention.
FIG. 7A illustrates an "external" optomechanical biometric sensor
module, according to some embodiments of the present invention.
FIG. 7B is a top plan view of the sensor module of FIG. 7A.
FIG. 7C is a cross-sectional view of the sensor module of FIG. 7B
taken along lines 7C-7C in FIG. 7B.
FIG. 7D is a cross-sectional view of the sensor module of FIG. 7B
taken along lines 7D-7D in FIG. 7B.
FIGS. 8A-8B are exploded views of an internal optomechanical
biometric sensor module, according to some embodiments of the
present invention.
FIG. 9A is a front perspective view of the sensor module of FIGS.
8A-8B in an assembled configuration.
FIG. 9B is a cross-sectional view of the sensor module of FIG. 9A
illustrating the biometric information pathways.
FIG. 9C is a cross-sectional view of the sensor module of FIG. 9A
illustrating the motion information pathways.
FIG. 9D is an enlarged cross-sectional view of the sensor module of
FIG. 9A illustrating the motion information pathways.
FIG. 10A illustrates an "internal" optomechanical biometric sensor
module, according to some embodiments of the present invention.
FIG. 10B is a cross-sectional view of the sensor module of FIG. 10A
taken along lines 10B-10B and illustrating the biometric
information pathways.
FIG. 10C is a cross-sectional view of the sensor module of FIG. 10A
taken along lines 10C-10C and illustrating the motion information
pathways.
FIG. 11A illustrates an "internal" optomechanical biometric sensor
module, according to some embodiments of the present invention.
FIG. 11B is a cross-sectional view of the sensor module of FIG. 11A
taken along lines 11B-11B and illustrating the biometric
information pathways.
FIG. 11C-11D are cross-sectional views of the sensor module of FIG.
11A taken along lines 11C-11C and illustrating the motion
information pathways in an uncompressed and compressed
configuration, respectively.
FIG. 12A illustrates an "internal" mechanical biometric sensor
module, according to some embodiments of the present invention.
FIG. 12B is a cross-sectional view of the sensor module of FIG. 12A
taken along lines 12B-12B of FIG. 12A.
FIG. 12C is a cross-sectional view of the sensor module of FIG. 12A
taken along lines 12C-12C of FIG. 12A.
FIG. 13A illustrates a band for a wearable monitoring device having
an integrated pressure-sensing bladder, according to some
embodiments of the present invention.
FIG. 13B is a top perspective view of a pressure-sensing bladder
for a wearable device, according to some embodiments of the present
invention.
FIG. 13C is a top plan view of the pressure-sensing bladder of FIG.
13B.
FIG. 13D is a cross section view of the pressure-sensing bladder of
FIG. 13B and illustrating the bladder attached to a wristband of a
wearable device.
FIG. 13E is a bottom plan view of the pressure-sensing bladder of
FIG. 13B.
FIG. 13F illustrates a pressure sensing bladder that includes fluid
reservoirs and artificial blood vessels in fluid communication with
the fluid reservoirs, according to some embodiments of the present
invention.
FIGS. 14A-14B illustrate an array of optomechanical sensors secured
to an arm of a subject and configured to track gestural motion,
according to some embodiments of the present invention.
FIGS. 15A-15E are spectrograms of noise reference signals and
associated photoplethysmograms.
FIGS. 16A-16C are spectrograms illustrating real time noise removal
from a PPG signal.
FIG. 17 illustrates an optomechanical sensor module having a
subtractive filter and noise reference for removing noise from
noisy physiological signals, according to some embodiments of the
present invention.
FIG. 18 is a flowchart of operations for utilizing the
optomechanical sensor of FIG. 17.
FIGS. 19-20 illustrate "internal" optomechanical biometric sensor
modules, and motion information and biometric information pathways
generated thereby, for "one-touch" or acute sensing applications,
according to some embodiments of the present invention.
FIG. 21 illustrates an electronic device including a "one-touch" or
acute sensing optomechanical sensor module, according to some
embodiments of the present invention.
FIG. 22 is a cross-sectional view of the electronic device of FIG.
21, taken along line 22-22.
FIG. 23 is a flowchart of operations for implementing blood flow io
stimulation to improve PPG measurements, according to some
embodiments of the present invention.
FIG. 24 is a top plan view of a device having an optomechanical
sensor module and blood flow stimulators, according to some
embodiments of the present invention.
FIG. 25 is a cross-sectional view of an embodiment of the device of
FIG. 24, taken along line 25-25.
FIGS. 26A-26D illustrate an integrated micro-fabricated
optomechanical sensor module and processing steps for fabricating
the optomechanical sensor module, according to some embodiments of
the present invention.
FIG. 27 illustrates a system for generating high-quality PPG data
and communicating this data to a secondary device or system,
according to some embodiments of the present invention.
FIG. 28 is a cross-sectional view of an earpiece having multiple
optomechanical sensor modules integrated therein, according to some
embodiments of the present invention.
FIG. 29 is a top plan view of a device having an optomechanical
sensor module and blood flow stimulators, according to some
embodiments of the present invention.
FIGS. 30-32 are flowcharts of operations for generating
physiological assessments of a subject, according to some
embodiments of the present invention.
FIG. 33 is a graph of optical scatter (PPG) signal intensity and
bioluminescence signal intensity vs. measured skin temperature for
multiple optical excitation wavelengths, according to some
embodiments of the present invention.
FIG. 34 is a flowchart of operations for generating physiological
assessments of a subject, according to some embodiments of the
present invention.
DETAILED DESCRIPTION
The present invention will now be described more fully hereinafter
with reference to the accompanying figures, in which embodiments of
the to invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as
limited to the embodiments set forth herein. Like numbers refer to
like elements throughout. In the figures, certain layers,
components or features may be exaggerated for clarity, and broken
lines illustrate optional features or operations unless specified
otherwise. In addition, the sequence of operations (or steps) is
not limited to the order presented in the figures and/or claims
unless specifically indicated otherwise. Features described with
respect to one figure or embodiment can be associated with another
embodiment or figure although not specifically described or shown
as such.
It will be understood that when a feature or element is referred to
as being "on" another feature or element, it can be directly on the
other feature or element or intervening features and/or elements
may also be present. In contrast, when a feature or element is
referred to as being "directly on" another feature or element,
there are no intervening features or elements present. It will also
be understood that, when a feature or element is referred to as
being "secured", "connected", "attached" or "coupled" to another
feature or element, it can be directly secured, directly connected,
attached or coupled to the other feature or element or intervening
features or elements may be present. In contrast, when a feature or
element is referred to as being "directly secured", "directly
connected", "directly attached" or "directly coupled" to another
feature or element, there are no intervening features or elements
present. Although described or shown with respect to one
embodiment, the features and elements so described or shown can
apply to other embodiments.
The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise.
As used herein, the terms "comprise", "comprising", "comprises",
"include", "including", "includes", "have", "has", "having", or
variants thereof are open-ended, and include one or more stated
features, integers, elements, steps, components or functions but
does not preclude the presence or addition of one or more other
features, integers, elements, steps, components, functions or
groups thereof. Furthermore, as used herein, the common
abbreviation "e.g.", io which derives from the Latin phrase
"exempli gratia," may be used to introduce or specify a general
example or examples of a previously mentioned item, and is not
intended to be limiting of such item. The common abbreviation
"i.e.", which derives from the Latin phrase "id est," may be used
to specify a particular item from a more general recitation.
As used herein, the term "and/or" includes any and all combinations
of one or more of the associated listed items and may be
abbreviated as "/".
As used herein, phrases such as "between X and Y" and "between
about X and Y" should be interpreted to include X and Y. As used
herein, phrases such as "between about X and Y" mean "between about
X and about Y." As used herein, phrases such as "from about X to Y"
mean "from about X to about Y."
Spatially relative terms, such as "under", "below", "lower",
"over", "upper" and the like, may be used herein for ease of
description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if a device in the figures is inverted, elements
described as "under" or "beneath" other elements or features would
then be oriented "over" the other elements or features. Thus, the
exemplary term "under" can encompass both an orientation of over
and under. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly. Similarly, the terms
"upwardly", "downwardly", "vertical", "horizontal" and the like are
used herein for the purpose of explanation only unless specifically
indicated otherwise.
It will be understood that although the terms first and second are
used herein to describe various features or elements, these
features or elements should not be limited by these terms. These
terms are only used to distinguish one feature or element from
another feature or element. Thus, a first feature or element
discussed below could be termed a second feature or element, and
similarly, a second feature or element discussed below could be
termed a first feature or element without departing from the
teachings of the present invention.
Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the specification and relevant art and
should not be interpreted in an idealized or overly formal sense
unless expressly so defined herein. Well-known functions or
constructions may not be described in detail for brevity and/or
clarity.
The term "about", as used herein with respect to a value or number,
means that the value or number can vary more or less, for example
by +/-20%, +/-10%, +/-5%, +/-1%, +/-0.5%, +/-0.1%, etc.
The term "circuit", as used herein, refers to an entirely software
embodiment or an embodiment combining software and hardware
aspects, features and/or components (including, for example, a
processor and software associated therewith embedded therein and/or
executable by, for programmatically directing and/or performing
certain described actions, operations or method steps).
The term "photoplethysmography" (PPG), as used herein, refers to
the method generating optical plethysmogram information from at
least one region of the body and processing this information to
generate biometric information derived from the optical
plethysmogram information. A PPG sensor module refers to a small
module comprising at least one optical emitter, at least one
optical detector, and at least some signal processing electronics
(analog and/or digital) to process the electrical signal from the
optical detector. The PPG sensor module may additionally comprise
optomechanics (optics and mechanical support) as well as a noise
reference sensor, such as a motion sensor or the like, for
detecting motion noise information that can be processed along with
the optical detector information to attenuate motion artifacts from
the desired PPG signal. Other types of noise references, such as
environmental light (ambient light) noise references may also be
integrated within the PPG sensor module to help attenuate ambient
light noise from the desired PPG signal. When a plurality of
optical emitters and/or detectors are integrated into the PPG
sensor module, additional biometric information may be extracted,
such as the determination of blood analyte (blood constituent)
levels (such as oxygenated hemoglobin, deoxygenated hemoglobin,
carboxyhemoglobin, methemoglobin, bilirubin, and the like). PPG
sensor modules may be placed or worn across virtually any part or
region of the body having blood flow, but such modules may more
typically be proximal to the skin of an organism, such as the skin
of the ear, forehead, nose, neck, chest, limbs (arms & legs),
wrists, feet, digits (fingers & toes), or the like.
The term "metric", as used herein, generally refers to a
measurement or measurement system of a property, and a "sensor
metric" refers to a measurement or measurement system associated
with a sensor. The metric may comprise an identifier for a type of
measurement, a value of the measurement, and/or a diagnosis based
on the measurement. For example, a metric may comprise "blood
pressure", with a value of "120/80", and/or a diagnosis of
"normal".
The term "biometric", as used herein, refers to a metric associated
with physiological (biological) information. Thus, the term
"biometric sensor" and "physiological sensor" are synonymous. For
example, a "biometric optical sensor" may refer to an optical
sensor configured for physiological monitoring. The "optical
sensor" may refer to the optical detector itself or the complete
PPG sensor comprising the optical emitters, detectors, noise
references, and the like.
The terms "sensor", "sensing element", "sensor module", and
"biometric sensor module", as used herein, are interchangeable and
refer to a sensor element or group of sensor elements that may be
utilized to sense information, such as information (e.g.,
physiological information, body motion, etc.) from the body of a
subject and/or environmental information in a vicinity of the
subject. A sensor/sensing element/sensor module may comprise one or
more of the following: a detector element, an emitter element, a
processing element, optics, mechanical support, supporting
circuitry, and the like. Both a single sensor element and a
collection of sensor elements may be considered a sensor, a sensing
element, or a sensor module. Often times in this description, the
reference to a "sensor element" refers to a fundamental component
of a sensor module or discrete sensor, wherein the sensor module or
discrete sensor comprises multiple sensor elements.
The term "optical emitter", as used herein, may include a single
optical emitter and/or a plurality of separate optical emitters
that are associated with each other.
The term "optical detector", as used herein, may include a single
optical detector and/or a plurality of separate optical detectors
that are associated with each other.
The term "wearable sensor module", as used herein, refers to a
sensor module configured to be worn on or near the body of a
subject.
The terms "monitoring device" and "biometric monitoring device", as
used herein, are interchangeable and include any type of device,
article, or clothing that may be worn by and/or attached to a
subject and that includes at least one sensor/sensing
element/sensor module. Exemplary monitoring devices may be embodied
in an earpiece, a headpiece, a finger clip, a digit (finger or toe)
piece, a limb band (such as an arm band or leg band), an ankle
band, a wrist band, a nose piece, a sensor patch, eyewear (such as
glasses or shades), apparel (such as a shirt, hat, underwear,
etc.), a mouthpiece or tooth piece, contact lenses, or the
like.
The term "monitoring" refers to the act of measuring, quantifying,
qualifying, estimating, sensing, calculating, interpolating,
extrapolating, inferring, deducing, or any combination of these
actions. More generally, "monitoring" refers to a way of getting
information via one or more sensing elements. For example, "blood
health monitoring" includes monitoring blood gas levels, blood
hydration, and metabolite/electrolyte levels.
The term "headset", as used herein, is intended to include any type
of device or earpiece that may be attached to or near the ear (or
ears) of a user and may have various configurations, without
limitation. Headsets incorporating sensor modules, as described
herein, may include mono headsets (a device having only one earbud,
one earpiece, etc.) and stereo headsets (a device having two
earbuds, two earpieces, etc.), true wireless headsets (having two
wireless earpieces), earbuds, hearing aids, ear jewelry, face
masks, headbands, glasses or eyewear, and the like. In some
embodiments, the term "headset" may include broadly headset
elements that are not located on the head but are associated with
the headset. For example, in a "medallion" style wireless headset,
where the medallion comprises the wireless electronics and the
headphones are plugged into or hard-wired into the medallion, the
wearable is medallion would be considered part of the headset as a
whole. Similarly, in some cases, if a mobile phone or other mobile
device is intimately associated with a plugged-in headphone, then
the term "headset" may refer to the headphone-mobile device
combination. The terms "headset" and "earphone", as used herein,
are interchangeable.
The term "optomechanical", as used herein, refers to optical
modulation with respect to mechanical energy in the general sense.
The motion may be due to relative motion, absolute motion,
vibration, pressure, force, etc. For example, generally in these
inventions, the optomechanical sensor may be used to sense motion
artifacts caused by any form of mechanical energy.
The term "physiological" refers to matter or energy of or from the
body of a creature (e.g., humans, animals, etc.). In embodiments of
the present invention, the term "physiological" is intended to be
used broadly, covering both physical and psychological matter and
energy of or from the body of a creature.
The term "body" refers to the body of a subject (human or animal)
that may wear a monitoring device, according to embodiments of the
present invention.
The term "processor" is used broadly to refer to a signal processor
or computing system or processing or computing method which may be
localized or distributed. For example, a localized signal processor
may comprise one or more signal processors or processing methods
localized to a general location, such as to a wearable device.
Examples of such wearable devices may comprise an earpiece, a
headpiece, a finger clip, a digit (finger or toe) piece, a limb
band (such as an arm band or leg band), an ankle band, a wrist
band, a nose piece, a sensor patch, eyewear (such as glasses or
shades), apparel (such as a shirt, hat, underwear, etc.), a
mouthpiece or tooth piece, contact lenses, or the like, as well as
smartphones and other devices carried or worn by a person. Examples
of a distributed processor comprise "the cloud", the internet, a
remote database, a remote processor computer, a plurality of remote
processors or computers in communication with each other, or the
like, or processing methods distributed amongst one or more of
these elements. The key difference is that a distributed processor
may include delocalized elements, whereas a localized processor may
work independently of a distributed processing system. As a
specific example, microprocessors, microcontrollers, ASICs
(application specific integrated circuits), analog processing
circuitry, or digital signal processors are a few non-limiting
examples of physical signal processors that may be found in
wearable devices.
The term "remote" does not necessarily mean that a remote device is
a wireless device or that it is a long distance away from a device
in communication therewith. Rather, the term "remote" is intended
to reference a device or system that is distinct from another
device or system or that is not substantially reliant on another
device or system for core functionality. For example, a computer
wired to a wearable device may be considered a remote device, as
the two devices are distinct and/or not substantially reliant on
each other for core functionality. Notwithstanding the foregoing,
any wireless device (such as a portable device, for example) or
system (such as a remote database for example) is considered remote
to any other wireless device or system.
The terms "respiration rate" and "breathing rate", as used herein,
are interchangeable.
The terms "heart rate" and "pulse rate", as used herein, are
interchangeable.
The term "RRi" refers to "R-R interval" in a cardiac waveform
(i.e., an electrocardiogram, photoplethysmogram, or the like) of a
person. Generally, where heart rate is used in embodiments of the
present invention, RRi may also be applied in a similar manner.
However, RRi and heart rate are generally related in an inverse
fashion, such that 1/RRi=instantaneous heart rate.
The term "thermal communication", as used herein, includes one or
more of conductive transfer of thermal energy, convective transfer
of thermal energy, and radiative transfer of thermal energy.
Various biometric parameters and activity parameters may be
described herein by using the name of the parameter (such as "heart
rate", VO.sub.2max, and the like). Generally speaking, these names
may refer to instantaneous values, averaged values, or some other
processing of the associated parameter(s). For example, a breathing
rate of 14 BPM (breaths per minute) may refer to an instantaneous
measurement or an averaged measurement (for example, an average
breathing rate of 14 BPM as averaged over 5 minutes). Unless
"instantaneous", "average", or some other adjective is used to
describe the parameter, it should not be assumed that there is a
limitation with respect to the processing of the parameter.
In the following figures, various monitoring devices will be
illustrated and described for attachment to the ear or an appendage
of the human body, or even integrated within clothing. However, it
is to be understood that embodiments of the present invention are
not limited to those worn by humans. In addition, monitoring
devices according to embodiments of the present invention may be
worn at other locations of the body.
The ear is an ideal location for wearable health and environmental
monitors. The ear is a relatively immobile platform that does not
obstruct a person's movement or vision. Monitoring devices located
at an ear have, for example, access to the inner-ear canal and
tympanic membrane (for measuring core body temperature), muscle
tissue (for monitoring muscle tension), the pinna, earlobe, and
elsewhere (for monitoring blood gas levels), the region behind the
ear (for measuring skin temperature and galvanic skin response),
and the internal carotid artery (for measuring cardiopulmonary
functioning), etc. The ear is also at or near the point of exposure
to: environmental breathable toxicants of interest (volatile
organic compounds, pollution, etc.); noise pollution experienced by
the ear; and lighting conditions for the eye. Furthermore, as the
ear canal is naturally designed for transmitting acoustical energy,
the ear provides a good location for monitoring internal sounds,
such as heartbeat, breathing rate, and mouth motion. Accurate
sensing of photoplethysmograms and heart rate from the ear has been
demonstrated in regions between the concha and anti-tragus
locations of the outer ear, and elsewhere at the ear.
Optical coupling into the blood vessels of the ear may vary between
individuals. As used herein, the term "coupling" refers to the
interaction or communication between excitation energy (such as
light) entering or exiting a region and the region itself. For
example, one form of optical coupling may be the interaction
between excitation light generated from within an optical sensor of
an earbud (or other device positioned at or within an ear) and the
blood vessels of the ear. In one embodiment, this interaction may
involve excitation light entering the ear region and scattering
from a blood vessel in the ear such that the temporal change in
intensity of scattered light is proportional to a temporal change
in blood flow within the blood vessel. Another form of optical
coupling may be the interaction between excitation light generated
by an optical emitter within an earbud and a light-guiding region
of the earbud. Thus, an earbud with integrated light-guiding
capabilities, wherein light can be guided to multiple and/or select
regions along the earbud, can assure that each individual wearing
the earbud will generate an optical signal related to blood flow
through the blood vessels. Optical coupling of light to a
particular ear region of one person may not yield
photoplethysmographic signals for each person. Therefore, coupling
light to multiple regions may assure that at least one
blood-vessel-rich region will be interrogated for each person
wearing an earbud. Coupling multiple regions of the ear to light
may also be accomplished by diffusing light from a light source
within an earbud.
Another example of optical coupling is the coupling of scattered
light from the body of a subject to light-guiding optics that guide
light towards a photodetector. The term "coupling", however, may
also refer to mechanical coupling, electrical coupling,
optomechanical coupling, or the like, and not just optical
coupling. As an example of optomechanical coupling, the optical
coupling of a light guide from an optical emitter to the body of a
subject may also be associated with the mechanical coupling of the
light guide (or of another optical pathway) to the body of a
subject.
Referring to FIGS. 1-6, biometric sensor modules 10 that may be
incorporated into various wearable devices are illustrated. The
illustrated sensor modules 10 may be integrated into various
wearable devices/apparel including, but not limited to, an earbud,
a wristband, an armband, a smartphone, clothing and accessory
apparel, or any other wearable form-factor for a digit, limb,
torso, head, ear, face, and the like. Each sensor module 10 is
configured to capture motion information from the body of a subject
via optomechanical coupling between the body and the sensor module
10. The captured motion information serves as a noise reference for
filtering motion noise (motion artifacts) from biometric sensor
signals. In the embodiment illustrated in FIG. 1, a sensor module
(e.g., a PPG sensor module, etc.) 10 includes a base 12, such as a
printed circuit board (PCB), that supports first and second optical
emitters 14, 16, and an optical detector 18. An optical barrier 20
is provided to prevent light emitted by the emitter 16 from
directly entering or saturating the optical detector 18. The
illustrated sensor module 10 also includes a stabilizer member 22
that is configured to transfer motion information from the body of
a subject wearing the sensor module 10 to the optical detector 18.
The stabilizer member 22 may also be referred to as a light
modulating (or light regulating) mechanism. In addition to helping
transfer subject motion information caused by mechanical energy
(i.e., the force of the subject body against the stabilizer member
22 as a result of subject motion), the stabilizer member 22 may
also be configured to help stabilize the sensor module 10 against
the skin.
The physical dimensions of the biometric sensor modules of FIGS.
1-6 are such that they are small enough to be wearable but large
enough to support the optics, electronics, and powering components.
Considering a top-view, typical dimensions for the modules may be
on the order of .about.1 mm-20 mm in length/diameter and the
associated optics may be on the order of 100 microns-3 mm in length
diameter. However, smaller and larger sizes may be utilized, and
embodiments of the present invention are not limited to any
particular sizes or dimensions.
The illustrated sensor module 10 produces two optical pathways 30,
40. The first optical pathway 30 (also referred to as the "motion
information pathway") is created by light emitted by the first
optical emitter 12 and reflected off of the stabilizer member 22.
The second pathway 40 (also referred to as the "biometric
information pathway") is created by light emitted by the second
optical emitter 16 that is absorbed, scattered, and/or reflected by
tissue, blood vessels, etc., within the body of the subject. The
biometric information pathway 40 contains a higher level of subject
physiological information than the motion information pathway 30,
which contains a higher level of subject motion information.
The embodiment illustrated in FIG. 2 is similar to the embodiment
of FIG. 1 except that a single optical emitter is utilized to
create both the motion information optical pathway 30 and the
biometric information optical pathway 40. The illustrated sensor
module (e.g., a PPG sensor module, etc.) 10 includes a base 12,
such as a PCB, an optical emitter 14, first and second optical
detectors 18, 24, and an optical barrier 20. As discussed above,
the optical barrier 20 is configured to prevent light emitted by
the emitter 14 from directly entering/saturating the optical
detector 18. The illustrated sensor module 10 also includes a
stabilizer member 22 that is configured to transfer motion
information from the body of a subject wearing the biometric sensor
module 10, as well as stabilize the biometric monitor 10 relative
to the skin of the subject. As with the embodiment of FIG. 1, the
illustrated sensor module 10 produces a motion information pathway
30 and a biometric information pathway 40. The emitter 14 is
configured to direct light towards the stabilizer member 22 to
create the motion information pathway 30 and is also configured to
direct light towards the skin of the subject such that the light
can be absorbed, scattered, and/or reflected by tissue, blood
vessels, etc., within the body of the subject.
The embodiment illustrated in FIG. 3 is similar to the embodiment
of FIG. 1 except that a stabilizer member is not utilized. The
illustrated sensor module (e.g., a PPG sensor module, etc.) 10
includes a base 12, such as a PCB, supporting first and second
optical emitters 14, 16, and optical detector 18, and an optical
barrier 20. As discussed above, the optical barrier 20 is
configured to prevent light emitted by the emitter 16 from directly
entering/saturating the optical detector 18. As with the embodiment
of FIG. 1, the illustrated sensor module 10 produces a motion
information optical pathway 30 and a biometric information optical
pathway 40. However, the motion information pathway 30 is created
by the first emitter 14 directing light towards the subject so that
the light reflects directly off of the skin, without substantial
interaction with blood flow-rich tissue, and is detected by the
optical detector 18.
The embodiment illustrated in FIG. 4 is similar to the embodiment
of FIG. 2 except that a stabilizer member is not utilized. The
illustrated sensor module (e.g., a PPG sensor module, etc.) 10
includes a base 12, such as a PCB, supporting an optical emitter
14, first and second optical detectors 18, 24, and an optical
barrier 20. As discussed above, the optical barrier 20 is
configured to prevent light emitted by the emitter 16 from directly
entering/saturating the optical detector 18. As with the embodiment
of FIG. 2, the illustrated sensor module 10 produces a motion
information optical pathway 30 and a biometric information optical
pathway 40. However, the motion information pathway 30 is created
by the emitter 14 directing light towards the subject so that the
light reflects directly off of the skin, without substantial
interaction with blood flow-rich tissue, and is detected by the
optical detector 18. The single emitter 14 is also configured to
direct light towards the skin of the subject such that the light
can be absorbed, scattered, and/or reflected by tissue, blood
vessels, etc., within the skin of the subject.
The sensor modules illustrated in FIGS. 1 and 2 are referred to as
"internal" optomechanical sensor modules (because the motion
pathway modulation happens via an internal motion, i.e., the
stabilizer member motion), and the sensor modules of FIGS. 3 and 4
are referred to as "external" optomechanical sensor modules
(because the motion pathway modulation happens via an external
motion, i.e., motion between the skin and the body). Each of the
embodiments illustrated in FIGS. 1-4 work by physically modulating
light in response to motion between the body of the subject wearing
the sensor module 10 and the sensor module 10. In FIGS. 1 and 2,
the stabilizer member 22 is used to transfer motion information
from the body of the subject via the motion information pathway 30.
In contrast, for the "external" embodiments of FIGS. 3 and 4,
physical modulation is achieved by relative motion between the body
of the subject and the biometric sensor module 10, itself.
In each of the embodiments of FIGS. 1-4, the motion information
pathway 30 contains little or no physiological information. As
such, by processing the two separate signals created by the two
optical pathways (i.e., the motion information pathway 30 and the
biometric information pathway 40) via a circuit or processor,
motion noise information may be attenuated and the biometric signal
information may be preserved or amplified. In some embodiments, the
attenuation of motion artifacts, by processing the two separate
signals, may be executed in analog space (via analog comparator
methods, differential amplification, analog adaptive filtering, or
the like) or in digital space (via spectral subtraction, digital
adaptive filtering, variable filtering, or the like).
For embodiments as illustrated in FIGS. 1-4, it should be noted
that, because the signal pathways for biometrics 40 and motion 30
are distinct, modulation of the electrical power feeding the
optical emitter(s) is not critical for embodiments of the present
invention to operate. Thus, embodiments of the present invention
may work during steady state (DC) powering conditions without
modulating power to the optical emitter or detector. However,
modulating the optical emitters is indeed permitted in these
configurations and may be useful for digital signal processing (in
general) and for removing ambient light noise. As a specific
example, ambient light may be attenuated from a PPG signal output
by subtracting optical detector signals collected when the optical
emitter is shut off from optical detector signals collected when
the optical emitter is turned on. As another example, for the
embodiments having at least two optical emitters (such as
illustrated in FIGS. 1 and 3), the emitters may be modulated in an
alternating fashion, where only one emitter is generating light at
a given time. This may help prevent optical cross-talk from
contaminating the optical detector readings when assessing the
biometric signal pathway 40 vs. the motion signal pathway 30.
Referring to FIG. 5, an external optomechanical sensor module
(e.g., a PPG sensor module, etc.) 10, according to other
embodiments of the present invention, is illustrated. The
illustrated sensor module 10 may be integrated into various
wearable devices including, but not limited to, an earbud, a
wristband, an armband, a smartphone, or any wearable form-factor
for a digit, limb, torso, head, ear, face, and the like. The
embodiment illustrated in FIG. 5 is similar to the embodiment of
FIG. 3 except that various optical elements (e.g., an optical
filter, an optical lens, etc.) are utilized with the optical
emitters 14, 16, and with the detector 18. For example, one or more
optical elements 15 are associated with the emitter 14 to help
steer light so as to be reflected from the skin of the user to
generate the motion information optical pathway 30. One or more
optical elements 17 are associated with the emitter 17 to help
steer light so as to enter the skin of the subject and to generate
the biometric information optical pathway 40. One or more optical
elements 19 are associated with the optical detector and facilitate
detection of the light from each of the motion information pathway
30 and the biometric information pathway 40. Examples of suitable
optical elements include light guides, light reflectors, light
cladding, or the like. In the illustrated embodiment, a barrier 20
is positioned between the detector 18 and each of the emitters 14,
16, and each barrier 20 is configured to prevent light emitted by
the emitters 14, 16 from directly entering/saturating the optical
detector 18.
It should be noted that a combined external and internal
optomechanical sensor module may also be produced by combining
external pathway components and internal pathway components on the
same module. In such case, it may be preferable to have at least
one optical detector associated with each pathway, such that at
least one detector is associated with the external pathway and at
least one detector is associated with the internal pathway.
Alternatively, one detector may be used by alternately powering the
emitters associated with each pathway, such that a single emitter
(or multiple emitters) from only one pathway is powered on at any
given time.
In other embodiments of the present invention, as illustrated in
FIG. 6, an internal optomechanical sensor module 10 may generate
both a motion sensing pathway 30 and a biometric signal pathway 40
via a single optical emitter 14 and a single optical detector 18.
The illustrated sensor module 10 may be integrated into various
wearable devices including, but not limited to, an earbud, a
wristband, an armband, a smartphone, or any wearable form-factor
for a digit, limb, torso, head, ear, face, and the like. A
stabilizer member 26 incorporates one or more optical filters to
pass, block, or scatter distinguishable wavelengths or wavelength
bands. For example, some optical wavelengths from the optical
emitter 14 may pass through the stabilizer member 26 and pass
through the biometric signal pathway 40, whereas other optical
wavelengths may be scattered by the stabilizer member 26 and pass
through the motion sensing pathway.
In the illustrated embodiment, the optical emitter 14 is configured
to generate at least two distinguishable wavelengths of
electromagnetic energy at distinguishably separate time periods,
and/or the optical detector 18 is configured to discriminate
between at least two distinguishable wavelengths. For example, the
optical emitter 14 may comprise at least two separate emitters
(such as with an LED array or mesa array, etc.) which alternate
emission intensity in time, and the detector 18 may be configured
to sense each wavelength separately in time. As another example,
the optical emitter 14 may be configured to generate multiple
wavelengths simultaneously (i.e., not alternating in time), and the
detector 18 may comprise at least two distinct detecting regions
(such as photodiodes or mesa arrays, etc.) each associated with a
different optical filter, such that the detector 18 can sense each
wavelength simultaneously via a separate detecting region or
"channel". An important benefit of the internal optomechanical
sensor configuration of FIG. 6 is that a single optical emitter and
single optical detector may be used, unlike the embodiments
presented in FIG. 1 and FIG. 2.
Referring now to FIGS. 7A-7D, an "external" optomechanical sensor
module (e.g., a PPG sensor module, etc.) 100 that can generate both
a motion information optical pathway 30 and a biometric information
optical pathway 40, io according to some embodiments of the present
invention, is illustrated. The illustrated biometric sensor module
100 may be integrated into various wearable devices including, but
not limited to, an earbud, a wristband, an armband, a smartphone or
any wearable form-factor for a digit, limb, torso, head, ear, face,
and the like. The illustrated sensor module 100 includes a housing
102 with a generally rectangular configuration. However,
embodiments of the present invention are not limited to the
illustrated configuration of the biometric sensor module 100. The
sensor module 100 may have any shape, such as triangular,
polygonal, round, etc. The housing 102 may be formed of
substantially opaque material.
The size of the sensor module 100 may be determined in part by the
location of the body where the sensor module 100 is positioned. For
example, a smaller sensor module 100 may be better suited for the
ear or along a muscle group, whereas a larger sensor module 100 may
be better suited for a flat surface, such as the wrist or forearm,
etc. However, the sensor module 100 should ideally be configured to
be small enough to not "rock" on multiple muscle groups as they
independently flex.
Within the sensor module housing 102 is a base 110, such as a PCB,
that supports a first pair of optical emitters 112, a second pair
of optical emitters 114, and an optical detector 116. Exemplary
optical emitters 112, 114 include, but are not limited to
light-emitting diodes (LEDs), laser diodes (LDs), compact
incandescent bulbs, organic LEDs (OLEDs), micro-plasma emitters, IR
blackbody sources, or the like. A light guide 120 is in optical
communication with each optical emitter 112 and is shaped and
configured to direct light emitted from each emitter 112 into the
skin of a subject wearing the sensor module 100 so as to generate a
biometric information pathway 40 (FIG. 7D). A light guide 130 is in
optical communication with each optical emitter 114 and is shaped
and configured to direct light so as to be reflected off of the
skin of the subject and to create a motion information pathway 30
(FIG. 7D).
A light guide 140 is in optical communication with the detector 114
and is configured to collect light from both the motion information
pathway 30 and the biometric information pathway 40 and deliver
collected light to the optical detector 114. In some embodiments,
the light guide 140 may include reflective material along the
sidewalls thereof to facilitate directing light to the optical
detector. In addition, the light guide 140 may have various shapes
and configurations that can be used to collect light for
detection.
The illustrated sensor module 100 also includes a plurality of
stabilizer members 150 that are configured to stabilize the sensor
module 100 when in contact with the skin of a subject. The light
guides 120, 130, the detector light guide 140, and the plurality of
stabilizer members 150 extend outwardly from the housing 102
through respective apertures formed within the outer surface 104 of
the housing 102, as illustrated. It should be noted that, in this
particular embodiment, the stabilizer members 150 are not
configured to modulate a motion pathway. Namely, these stabilizers
150 are used solely for stabilizing the sensor module 100 against
the body of the subject.
In use, the sensor module 100 is positioned against the skin of a
subject, for example via a strap or band, and optical emitters 112
emit light through light guides 120 and into the body. The light
propagates through the body and then enters the light guide 140
that directs the light to the light detector 116. Optical emitters
114 emit light through light guides 130 which direct the light to
reflect off of the body of the subject and enter the light guide
140 so as to be detected by the detector 116 and substantially
without entering the body. Light from the optical emitters 112 is
turned on (modulated) at different times from light from the
optical emitters 114 and the detector 116 is able to discriminate
light containing biometric information (i.e., light in the
biometric information pathway 40) from light containing motion
information (i.e., light in the motion information pathway 30).
Signals generated by the light detector 116 for detected light
containing motion information and detected light containing
biometric information are sent to a processor and, together with
any other reference signals, used to extract purely biometric
information.
In one mode of operation, the emitters 112, 114 may be alternately
modulated in time, such as with pulsing or biasing, such that
signal processing can be used to identify motion information in the
motion information pathway 30 and biometric information in the
biometric information pathway 40. Then, an analog or digital filter
may be implemented to process both the motion information and
biometric information to selectively attenuate motion artifact
information from the biometric information.
Light in the motion information pathway 30 is modulated mostly by
motion artifacts, such as optical scatter from the skin interface,
as the sensor module housing 102 moves up and down and side-to-side
against the skin of the subject wearing the sensor module 100. In
contrast, light in the biometric information pathway may be both
physically modulated by subject motion and physiologically
modulated by being absorbed, scattered, and/or reflected by tissue,
blood vessels, etc., within the body of the subject.
In some embodiments, the optical emitters 114 may emit light at a
shorter wavelength than light emitted by the optical emitters 112.
Shorter wavelength light may not penetrate as deeply into the skin
as longer wavelength light, thereby reducing the intensity of
biometric information in the motion information pathway 30. In some
embodiments, optical emitters 114 emit light at optical wavelengths
shorter than 470 nm. In other embodiments, optical emitters 114
emit light at optical wavelengths shorter than 420 nm. However,
optical emitters that can emit light at any optical wavelength can
be used for the emitters 114, including wavelengths longer than
that generated by the optical emitters 112 in the biometric signal
pathway. However, wavelengths shorter than 280 nanometers and
longer than 5 microns may be more challenging to effectively
implement partly due to high absorption of the shorter wavelengths
and waveguiding effects at larger wavelengths. Moreover, solid
state optical detectors may exhibit extremely low sensitivity for
wavelengths shorter than 280 nanometers and may be extremely noisy
(especially at room temperature and higher) for wavelengths greater
than 2 microns.
As discussed above, some biometric information (e.g., PPG
information) may be included in the motion information pathway 30
because at least some light may interact with blood flow at the
skin surface. As a result scattered light received by the detector
116 may at least partially comprise biometric information, which is
undesirable, as in such case it may be difficult to use the motion
pathway signal as a noise reference for cleaning up a
photoplethysmogram. Thus, in some embodiments of the present
invention, the light guides 130 are configured such that light
emitted by the optical emitters 114 is steered to scatter from the
skin at large angles which may discourage absorption at the skin.
As illustrated in FIG. 7D, the senor module 100 is configured such
that light scatters from light guide 130 to propagate towards the
skin at a large angle and scatter off and/or guide along the skin
surface towards io the detector light guide 140.
Referring now to FIGS. 8A-8B and FIGS. 9A-9D, an "internal"
optomechanical sensor module (e.g., a PPG sensor module, etc.) 200
that can generate both a motion information optical pathway 30 and
a biometric information optical pathway 40, according to some
embodiments of the present invention, is illustrated. The
illustrated biometric sensor module 200 may be integrated into
various wearable devices including, but not limited to, an earbud,
a wristband, an armband, a smartphone or any wearable form-factor
for a digit, limb, torso, head, ear, face, and the like. The
illustrated sensor module 200 includes a housing 202 having first
and second portions 204, 206 that are secured together via
fasteners F. In the illustrated embodiment, each fastener F is a
screw or other threaded member that is inserted through the housing
second portion 206 and threadingly engages a threaded insert 207
secured to the first housing portion 204. However, embodiments of
the present invention are not limited to the use of threaded
fasteners. Various ways may be utilized to secure the housing first
and second portions 204, 206 together, as would be understood by
one skilled in the art. In some embodiments, one or both of the
housing first and second portions 204, 206 are formed of
substantially opaque material to help prevent ambient light
intrusion and hence optical signal corruption.
The illustrated sensor module 200 has a generally round
configuration. However, embodiments of the present invention are
not limited to the illustrated configuration of the sensor module
200. The sensor module 200 may have any shape, such as triangular,
polygonal, rectangular, etc. In addition, the size of the sensor
module 200 may be determined in part by the location of the body
where the sensor module 200 is positioned. For example, a smaller
sensor module 200 may be better suited for the ear or along a
muscle group, whereas a larger sensor module 100 may be better
suited for a flat surface, such as the wrist or forearm. However,
the sensor module 200 should ideally be small enough to not "rock"
on multiple muscle groups as they independently flex.
Positioned within the housing 202 of the sensor module 200 is a
base 210, such as a PCB, that supports optical emitters 212, 214
and optical detector 216. Also positioned within the housing 202 is
a light guide 220 that is configured to be in optical communication
with optical emitters 212, a stabilizer pad 230, and a light guide
240 that is configured to be in optical communication io with the
optical detector 216.
The illustrated light guide 220 includes a plurality of elements
222 extending outwardly from one side thereof that are configured
to extend through respective apertures 203 in the first housing
portion 204. These elements 222 are not meant to transfer motion
information, unlike stabilizing members 232 and 234, but rather are
used for stabilizing (supporting) the sensor at the body.
The light guide 220 also includes elements 224 that extend through
apertures 205 in the first housing portion 204 that are configured
to guide light from emitters 212 into the body of a subject wearing
the sensor module 200. The light guide 220 is also configured to
internally guide light from the emitters 214 towards the stabilizer
members 232, 234 of the stabilizer pad 230.
The illustrated stabilizer pad 230 includes a first pair of
stabilizer members 232 extending outwardly therefrom that are
configured to extend through respective apertures 207 in the first
housing portion 204. The illustrated stabilizer pad 230 also
includes two pair of stabilizer members 234 extending outwardly
therefrom that are configured to extend through respective
apertures 209 in the first housing portion 204. The stabilizer
members 232, 234 are configured to contact the skin of a subject
and move in response to subject motion. Light from the optical
emitters 214 is directed towards the stabilizer members 232, 234
via either the light guide 220 or via an empty pocket in the pad
230 in order to create respective motion information pathways 30,
as will be described below.
In the illustrated embodiment, the light guide 220 and stabilizer
pad 230 are integrated as one unit and referred to as a
"multi-shot" lens. The illustrated multi-shot lens may be
fabricated by directing two types of plastic into a mold
(transparent+opaque), such that there are no seams between the two
regions. As a result, the multi-shot lens can prevent the leakage
of moisture, such as sweat from a subject wearing the sensor module
200, into the electronics. The transparent portion of the lens is
configured for light guiding. The opaque region is configured for
optomechanical sensing (i.e., motion sensing) as described above.
However, in other embodiments, the light guide 220 and stabilizer
pad 230 may be separate elements.
Referring now to FIG. 9A, the sensor module 200 of FIGS. 8A-8B is
illustrated in an assembled configuration. The stabilizer members
232, 234 extend through the housing first portion, as illustrated.
The stabilizer members 232, 234 interact with the skin of a subject
wearing the sensor module 200 and are configured to compress
downwardly against the light guide 220 as a result of subject
motion and modulate light emitted by optical emitters 214 to
produce motion information optical pathways (e.g., 30, FIGS. 1-2)
that are detected by the optical detector 216. The stabilizer
members 232, 234 are configured to change shape (i.e., collapse) in
proportion to relative motion between the skin and the sensor
module 200. For example, this relative motion may be caused by
force applied upon the stabilizer members 232, 234 by the body of
the user. When a stabilizer member 232, 234 collapses, it may
modulate light between the optomechanical emitters 214 and the
detector 216 in proportion to this relative motion. Thus, whereas
the external optomechanical sensor light guides 120, 130 of the
sensor module of FIGS. 7A-7D may be made of rigid optically
transparent material, so that bending of the optics will not
distort the desired reflection profile of scattered light, in
contrast, the internal optomechanical sensor module 200 utilizes
stabilizer members 232, 234 that are made of material that is at
least partially compliant (pliable) upon a pressure between the
sensor module 200 and the skin/body.
FIG. 9B is a cross-sectional view of the sensor module 200 of FIG.
9A and illustrates the configuration of the light guide 220 that
creates the biometric information optical pathway that allows light
emitted from the optical emitters 212 to enter the body of the
subject and then be collected and detected by the detector 216.
FIG. 9C is a cross-sectional view of the sensor module 200 of FIG.
9A and that illustrates the configuration of the light guide 220
that creates the motion information optical pathways that allows
light emitted from the optical emitters 214 to be modulated by the
stabilizer members 232, 234 and then be detected by the detector
216. Motion information pathways 30 produced by the sensor module
200 are illustrated in FIG. 9D.
During relative motion between the sensor module 200 and the body
of a subject wearing the sensor module, light scattered via the
motion information pathways and light scattered by the biometric
information pathways may both comprise motion artifact information.
The linearity of motion artifact information from these optical
pathways may be at least partially determined by the compliance of
the stabilizer members 232, 234 used. Generally, a higher linearity
between these pathways may be realized when the compliance of the
stabilizer members 232, 234 is close to that of the skin of the
subject. This is because light scattered from a biometric
information pathway may be scattered mostly by the skin and/or
other tissue near the skin of the user, and thus stabilizer members
232, 234 having a mechanical compliance similar with that of skin
may also scatter light in a similar manner during motion. It should
be noted that although the motion information pathways 30 in FIG.
9D do not contain any light guiding material (e.g., they are filled
with air or a vacuum), the motion information pathways may be
filled with light guiding material instead. Moreover, this
light-guiding material may also be rigid (such as glass) or
compliant (such as silicone).
For the embodiments illustrated in FIGS. 1-6, 7A-7D, 8A-8B and
9A-9D, physical dimensions of housings for these embodiments may be
on the order of about 5-20 millimeters, and the physical dimensions
of the optical emitter and detector components may be on the order
of 0.5-3 mm. However, embodiments of the present invention are not
limited to any particular housing size/configuration or optical
emitter/detector size/configuration. Numerous size configurations
are suitable for embodiments of the present invention. Some size
limitations of note are that the ideal spacing between emitters and
detectors in a biometric signal pathway may be in between 2 mm and
7 mm. Generally speaking, the farther the emitter-to-detector
spacing, the higher the signal-to-noise (AC/DC) ratio. However, if
the spacing is too far, the biometric signal will be too weak to be
above the noise floor of the photodetector. Also, the sizing of
optics in the embodiments of FIGS. 1-6, 7A-7D, 8A-8B and 9A-9D may
ideally be larger than a few tens of microns, so that the optics
can capture enough light and not overly attenuate signals.
Referring now to FIGS. 10A-10C, an internal optomechanical sensor
module (e.g., a PPG sensor module, etc.) 300, according to other
embodiments of the present invention, is illustrated. The
illustrated sensor module 300 includes a light guide 320 having
three separate portions 320a, 320b, 320c separated by optical
barriers 330. FIG. 10B is a cross-sectional view of the sensor
module 300 of FIG. 10A taken along lines 10B-10B and illustrates
the biometric information pathways 40. The light guide 320 is
configured to allow light emitted from the optical emitters 312 to
enter the body of the subject and then be collected and io detected
by the detector 316 in order to create biometric information
pathways.
FIG. 10C is a cross-sectional view of the sensor module 300 of FIG.
10A taken along lines 10C-10C and illustrates the motion
information pathways 30. Stabilizer members 332 are configured to
modulate with motion at the sensor module/skin interface. As the
interface force increases on a stabilizer member 332, the gap
decreases thereby reducing the amount of light reaching the optical
detector 316. The modulation of the amount of light reaching the
optical detector 316 can be correlated to subject motion and a
motion reference signal can be generated via a processor.
Referring now to FIGS. 11A-11D, an internal optomechanical sensor
module (e.g., a PPG sensor module, etc.) 400, according to other
embodiments of the present invention, is illustrated. The
illustrated sensor module 400 includes a base 410, such as a
printed circuit board (PCB), supporting a pair of optical emitters
412 and an optical detector 416. The sensor module 400 also
includes a compressible/deformable member 420 that contains a
plurality of internal light-shuttering channels or pathways 422. In
FIG. 11C, there is only a light external pressure on the
compressible/deformable member 420 of the sensor module 400. As a
result, the light-shuttering pathways 422 remain expanded allowing
a maximum amount of light therethrough to the optical detector 416.
In FIG. 11D, force on the compressible/deformable member 420 has
increased due to subject motion. As a result, the light-shuttering
pathways 422 are compressed decreasing the amount of light that can
pass therethrough to the optical detector. The modulation of the
amount of light reaching the optical detector 416 can be correlated
to subject motion and a motion reference signal can be generated
via a processor.
Referring now to FIGS. 12A-12C, a biometric sensor module 500 that
includes an internal mechanical apparatus (e.g., a pressure
transducer) 520 configured to capture motion information from the
body of a subject wearing the sensor module 500 is illustrated. The
illustrated sensor module 500 includes a base 510, such as a
printed circuit board (PCB), supporting a plurality of optical
emitters 512 and an optical detector 516. The sensor module 500
also includes a plurality of members 530 extending therefrom that
are configured to engage the skin of a subject wearing the sensor
module 500. Forces imparted upon the members 530 as a result of
subject motion are transferred to the pressure io transducer 520
and measured. The modulation of pressure in the pressure sensor can
be correlated to subject motion and a motion reference signal can
be generated via a processor.
Referring now to FIG. 13A, according to other embodiments of the
present invention, pressure variation information may be obtained
by wrapping a limb 600 of a subject with a fluid filled expansion
bladder 610, then constraining the bladder 600 to prevent expansion
away from the limb 600 with a band 620 having low or no compliance
(i.e., low or no stretchiness). The illustrated band 620 supports a
biometric sensor module 630, such as a PPG sensor module. The
non-stretchy (i.e., inelastic) band 620 can be incorporated as part
of the expansion bladder 610 itself by constructing the bladder 610
from a semi-compliant material. One example of this could be a
polyurethane coated nylon material that is RF welded together to
form a pouch. This type of a construction will allow some stretch,
but will retain a limited shape within the functional pressure
range and effectively function as a semi-constrained system.
Through this configuration, pressure changes within the limb of a
subject wearing the bladder 610 can be directly transferred to the
fluid filled pouch.
The fluid within the bladder 610 can be any suitably stable liquid,
gas, or gel (water, a water solution, air, silicone, colloid(s),
and the like), and pressure transducers (not illustrated) can be
employed within the bladder volume to transmit a signal
proportional to the change in internal pressure. Exemplary pressure
transducers include MEMS (micro-electromechanical systems) devices,
diaphragms, actuators, etc. In addition, an optical scatter sensor
(such an optomechanical pressure sensor) may be used to sense
optical scatter upon motion of the bladder 610 in proportion to
changes in pressure.
In order for the bladder 610 to interact with the limb 600 of the
subject to pick up pressure readings, it may be necessary for the
bladder 610 to interact with the limb 600 by maintaining good
surface interaction with the limb 600. Tightening the band 620
around the bladder 610 of fixed volume can force the bladder 610 to
interact with the limb 600 and experience deformation and pressure
changes from pressure changes within the limb 600. Without such
constraint, the bladder 610 may dislocate outside of the band 620
and parts of the bladder 610 may then not couple well with the limb
600. However, if a rigid or semi-rigid band does not fully surround
the bladder 610, a semi-constrained bladder system may also provide
good coupling between the limb 600 and the pressure sensitive
bladder 610. In such case, it may be necessary to pump or fill gas
(manually or automatically) within the bladder 610 to prevent
dislocation of the bladder 610 outside of the band 620.
The use of a compliant bladder, such as bladder 610 illustrated in
FIG. 13A, can be advantageous because a large surface area can
interact with the limb 600 over a large proportion of the surface
area of the limb 600. In the illustrated embodiment of FIG. 13A,
the bladder encircles the limb 600 and pressure changes relate to
compression of the entire cross-sectional area of the limb 600. In
this way, a processor associated with the PPG sensor 630 receives
information about the pressure changes throughout the entire limb
cross-sectional area as the limb 600 can be fully contained within
the pressure interrogation area. However, a partial bladder (non
circumferential) may also be used such that only part of the limb
600 can interact with the bladder 610. In such case, the bladder
610 may be preferably located near the site of the biometric sensor
location, such that the motion noise reference location (the
pressure sensing location) and biometric sensing location are in
proximity. Additionally, although FIG. 13A is drawn towards a limb
(such as an arm, wrist, leg, etc.), embodiments of the present
invention may be applied towards digits (fingers and toes) as well
as other parts of the body that can support an encircling or
partially encircling device.
Referring now to FIGS. 13B-13D, a modular bladder 640 according to
embodiments of the present invention is illustrated. A PPG sensor
module 630 is positioned on top of a substrate 650 (such as a
circuit board or other support structure having electrical
connections for powering the sensor module 630), and the substrate
650 may rest on top of the bladder 640. Thus, when integrated into
a wearable device (i.e., such as a wearable band 620, FIG. 13D),
the bladder 640 experiences a compressive force (i.e., pressure)
when the PPG sensor module 630 makes contact with the skin, pushing
on the substrate 650 and hence the bladder 640 in contact
therewith. A pressure sensor 660 in the bladder 640 detects this
pressure so that it can be used as a noise reference, as described
below with respect to FIG. 17.
The pressure sensor 660 may be any of a variety of different types
of pressure sensors that can be embedded in a wearable sensor
module, as described below. In addition, although one pressure
sensor 660 is shown, a plurality of pressure sensors may be
utilized.
FIGS. 13A-13E illustrate several concepts: 1) reducing pressure and
pressure changes on a sensor module, and 2) using the pressure
measurement of the bladder fluid as a noise reference of blood
occlusion. The changes of pressure of a sensor head, device case,
straps, and the like of a wearable device on the skin of a subject
tends to modulate the blood's proximity to the surface of the skin
by occlusion. More pressure tends to occlude blood away from the
surface, while less pressure allows the blood to move back towards
the surface. It can be advantageous to reduce and redistribute the
total pressure on the face of a sensor head against the skin of a
subject. The sensor head can be mounted with a fluid filled bladder
to act as a pressure absorber to reduce the pressure between sensor
head and the skin. The fluid can be air (or other suitably inert
gas), silicone, gel, liquid water (or other suitably inert liquid),
or the like. By shaping the bladder 640 of FIGS. 13B-13E as a ring
surrounding the sensor head/module 630, the pressure can be
redistributed equally across the sensor head/skin contact so as to
reduce spots of blood occlusion, especially at the corners or near
the optical path of the sensor head.
The bladder 640 also acts to reduce the rate of change of pressure
of the sensor head/module 630 against the skin, as happens during
vigorous activities or during muscle movements in the area of the
sensor head/module 630. The bladder 640 acts to reduce the
suddenness of change of pressure of the system. This is
advantageous for the sensor signal quality to avoid sudden changes
in measurements. A choice of bladder fluid may be made to most
effectively balance the pressure reducing effect overall, to most
effectively redistribute pressure, or to most effectively reduce
pressure changes.
Because PPG sensors are sensitive to changes in blood flow,
pressure-related blood flow may be a source of noise on the
measured optical signal of the sensor head/module 630 during motion
or muscle flexing during a user's activities. For example, flexing
muscles may push away blood in such a way that the resulting PPG
signal shows the characteristics of a heartbeat pulse wave during
muscle flexing, confusing algorithms designed to extract heart rate
from the PPG signal.
To allow an algorithm to account for this noise, it can be
advantageous to know the pressure of the sensor head/module 630
against the skin so that it may be used as a noise reference. The
amount of pressure inside the bladder 640 of FIGS. 13B-13E may be
directly related to the amount of pressure between the sensor
head/module 630 and the skin. By coupling a pressure sensor 660 to
the fluid within the bladder, the measurement can be estimated as a
measurement of the pressure of the blood occlusion force. A choice
of bladder fluid may be made to closely represent the fluid
dynamics of the skin/blood system such that it most closely
correlates with the contributing noise, such that noise subtraction
results in a cleaner PPG signal more closely related to
heartbeat-induced blood flow. For example, in the optomechanical
configuration of a pressure sensor, where an optical emitter shines
light into the fluid and an optical detector detects light
scattered from the fluid, wherein the scattered light intensity is
proportional to the fluid motion, the desired optical detector
signal would closely correlate with the unwanted venous blood
motion component (non-pulsatile component) of the blood flow signal
captured by the associated PPG sensor.
An exemplary configuration of such a representation is presented in
FIG. 13F, which illustrates a bladder 670 wherein the fluid-filled
region comprises artificial blood vessels 680 at least partially
filled with fluid 682. In such a configuration, the bladder may be
comprised of compliant (compressible) material, such as plastic,
polymer material, silicone, rubber, latex, or the like, such that a
compression of the material will result in a skin-like (i.e., human
skin-like) compression, pushing the fluid 682 from the artificial
fluid reservoirs 690 across the artificial vessels 680. Though the
artificial vessels 680 are shown as mostly lateral structures, they
may be orientated as mostly vertical structures or other
predominate directions, as with real human blood vessels. In one
non-limiting embodiment of FIG. 13F, the bladder 670 may be
constructed by molding silicone (or other suitable material) around
an artificial blood vessel mold. In another non-limiting
embodiment, the artificial blood vessels 680 may be fabricated by
molding silicone (or other suitable material) without the
artificial blood vessel molds in place. Rather, the blood vessel
structures may be fabricated by generating intentional bubbles in
the silicone. The fluid may be filled within the vessels 680 by
soaking the bladder 670 in fluid or exposing the bladder 670 to
fluid and sealing up the structure (such as by overmolding or the
io like) to create a non-leaking unit.
In another embodiment of FIG. 13F, the artificial structure (i.e.,
the bladder 670) may further comprise microfluidic or nanofluidic
circuits and structures to control the fluid flow within the
artificial structure. A variety of micro- and nano-fluidic circuits
and structures are well-known in the art. It should be noted that
the particular embodiment of FIG. 13F can be especially useful as a
noise reference for both heart rate monitoring and blood pressure
monitoring, as the pressure signal generated may be more indicative
of venous blood flow than the other embodiments of FIGS. 13A-13E.
Moreover, a further benefit of using the configuration of FIG. 13F
as a noise reference is that physical contact of the artificial
structure 670 with the skin may not be required, as fluid will flow
during motion and be sensed by the pressure (or optical) sensor
even without a pressure differential between a wearable device
utilizing the artificial structure 670 and the body of the
subject.
Referring now to FIGS. 14A-14B, a sensor module 700 having an array
of optomechanical motion noise reference sensors 710 (having, for
example, one or more of the optomechanical configurations described
in the various embodiments of the present invention) for tracking
gestural motion is illustrated. The sensor module 700 is attached
to the limb of the subject via a band 720. The optomechanical
motion sensors 710 are applied in an array along the body (in this
case a limb) to sense pressure or to sense motion changes between
the array elements and the body of the subject. Thus, as the
subject generates gestures, the array elements 710 may sense the
pressure generated by these gestures, and these signals may be
processed to recognize the gestures. Because the location of the
optomechanical sensors with respect to each other is known in
advance by their layout in the wearable device, a processor can
analyze the sensor readings to map out the muscle-movement-induced
pressure readings across the body, converting sensor information
into gestural information.
The wearable array may also be in communication with a local
accelerometer, and combined accelerometry data plus array data may
be processed to determine gross body part motion as well as
gestural motion. This functionality may be achieved because the
accelerometer may be configured to assess gross acceleration,
angular momentum, magnetic location, etc., whereas the array may be
configured to sense pressure signals from gestures. It should be
noted that in a strictly gestural monitoring system, a biometric
sensor is not necessarily needed, but an integrated biometric
sensor may also be added to the embodiment in order to provide
biometric sensing in addition to gestural sensing.
Head or ear motions or gestures also may be assessed via
embodiments of the present invention. One or more optomechanical
sensors or sensor arrays 710 may be integrated into an audio
earpiece and configured to measure scattered light signals from
body motion caused by footsteps, speaking, yawning, chewing, and
the like. The output of the optomechanical sensor may then be
processed to extract footsteps and mouth motions. Signals
associated with mouth motions may be processed to determine what
words a subject is speaking or what words someone is "mouthing"
(not technically speaking, but generating the mouth motions for a
word). These signals may then be used to control a user interface
or to be translated into true sounds. For example, by mouthing the
word for "turn on", the optomechanical sensor output may be
processed (locally or remotely) into a command to turn on a
smartphone, the earpiece itself, or some other device.
Reference is now made to FIGS. 15A-15E. FIG. 15E is a spectrogram
of a raw PPG signal collected from a person wearing a PPG sensor in
proximity of the person's skin. FIGS. 15A-15B show normalized
spectrograms for a PPG-derived heart rate signal, following active
motion-noise cancellation employing embodiments of the present
invention and embodiments of co-owned U.S. Patent Application
Publication Nos. 2014/0114147, 2015/0018636, and 2015/0011898,
which are incorporated herein by reference in their entireties.
A person wearing an armband having a PPG sensor module, according
to embodiments of the present invention, was exercising via a
strength training technique that involved the following exercises:
rowing, inchworms, and thrusters. The PPG armband comprised both an
inertial sensor (a 3-axis accelerometer) and an optomechanical
sensor (an internal optomechanical sensor). During the PPG signal
collection, frequencies associated with motion noise, and harmonics
thereof, were actively removed in real-time via spectral
subtraction and redaction as described in U.S. Patent Application
Publication Nos. 2014/0114147, 2015/0018636, and 2015/0011898.
FIGS. 15A-15B show the PPG spectrograms for this exercise session
following active noise removal. However, FIG. 15A shows the
spectrogram of the PPG signal where only the accelerometer was used
as a noise reference, and FIG. 15B shows the spectrogram of the PPG
signal where both the accelerometer and an optomechanical sensor
according to embodiments of the present invention were used as a
noise reference. Note that for FIG. 15B, the heart rate information
is clearly visible in the spectrogram for all exercises. However,
in FIG. 15A, the heart rate information for the first part of the
exercise, in this case rowing, was not adequately extracted. The
origin for this noteworthy difference between FIG. 15A and FIG. 15B
may be elucidated by viewing the normalized spectrograms of FIG.
15C, which is the z-axis of the accelerometer and FIG. 15D, which
is the optomechanical sensor output. Namely, the spectrogram of
optomechanical sensor output of FIG. 15D reflects the noise in the
raw PPG spectrogram of FIG. 15E much more closely (as is evinced by
the low frequency noise in FIG. 15E).
In contrast, the spectrogram of the accelerometer output does not
as closely reflect the noise characteristics of the raw PPG
spectrogram. Thus, subtraction of unwanted frequencies is more
effective when including the optomechanical information of FIG.
15D, yielding a more accurate representation of user heart rate
(FIG. 15B as opposed to FIG. 15A. For noise removal, it is
important to note that one may choose to use either the
accelerometer signal or the optomechanical signal to determine a
user cadence and then use this cadence information to determine
harmonics for redaction (i.e., redacting harmonics of running
cadence from the PPG signal). But each noise reference may be used
for spectral subtraction, either individually or combined.
It should be noted that a myriad of noise removal techniques may be
applied with the optomechanical pressure signal as a noise
reference. For example, the optomechanical signal may serve as the
input to an adaptive filter such that the noise reference is
actively removed from the raw PPG signal in real time. FIGS.
16A-16C are spectrograms illustrating real time noise removal from
a PPG signal. These spectrograms are intensity-normalized in each
time slice, and come from the same subject executing a
CROSSFIT.RTM.-style exercise test over the course of 600 seconds,
while the subject was wearing a PPG sensor having an internal
optomechanical sensor, as shown in FIGS. 9A-9D. FIG. 16A presents
io a spectrogram of a PPG signal (the biometric information)
following a DC-removal filter. A heart rate signal is barely
visible in this spectrogram, and motion noise is apparent. FIG. 16B
presents a spectrogram of the associated optomechanical signal (the
motion noise reference) following a DC-removal filter. The motion
noise is clearly present in the spectrogram. FIG. 16C presents a
spectrogram of the output of an adaptive filter (i.e., an LMS or
"least-mean-squares" adaptive filter) used to subtract the
optomechanical information from the PPG signal information in
accordance with embodiments of the present invention (removing the
features of FIG. 16B from that of FIG. 16A). Note that the heart
rate signal "pops out" from the spectrogram once the motion noise
is removed. In particular, the common noise between the optical
signal and the optomechanical signal (the noise less than 50 BPM)
is removed in FIG. 16C. Also, much of the motion noise between 50
and 80 BPM is removed between 230 and 350 seconds in FIG. 16C.
Exemplary adaptive filters are describe in co-owned U.S. Pat. Nos.
8,700,111 and 8,647,270, which are incorporated herein by reference
in their entireties. Moreover, as illustrated in FIG. 17, an
optomechanical sensor according to embodiments of the present
invention may be used first as a noise reference in a subtracting
time-domain adaptive filter, effectively removing or subtracting
motion noise from a PPG signal to generate a cleaner PPG signal,
and then this cleaned-up PPG output may be the input of a parameter
extractor using the accelerometer as a noise reference and/or using
the accelerometer to determine user cadence and implement
heuristics for estimating heart rate, as described in the
aforementioned U.S. patents. Optionally, the accelerometer may also
be used as a 2nd noise reference in the adaptive filter to further
clean up the PPG signal before the output reaches the parameter
extraction stage.
In the illustrated embodiment of FIG. 17, signals 900 and 902 from
a sensor module according to embodiments of the present invention
are input to a subtractive filter 904. Signal 900 is a signal
containing primarily physiological information from a subject
(i.e., physiological information obtained via a biometric
information optical pathway 40), and signal 902 containing
primarily subject motion information (i.e., motion information
obtained via a biometric information optical pathway 30). The
subtractive filter 904 removes motion noise from the biometric
signal using the motion information pathway signal as a noise
reference, and the cleaned-up biometric signal is input to the
parameter extractor 906 which is configured to produce digital data
strings including various physiological data.
Combined with the motion pathway information signal 902, the
accelerometer 908 associated with the sensor module may be used as
an additional noise reference and/or to determine user cadence and
implement heuristics for estimating heart rate. For example, as
shown in FIG. 17, motion information from both the accelerometer
908 and motion information pathway signal 902 may be subtracted
from the biometric information pathway signal 900. Similarly, both
the accelerometer 908 and motion information pathway signal 902 may
provide motion information to a processor as a basis for redacting
harmonics associated with body motion from the biometric pathway
signal.
Additionally, the accelerometer 908 signal and the motion
information pathway signal 902 may be processed by a processor such
that one of these signals filters or modifies the other signal.
This can be useful for the case where it is beneficial for the two
signals to have similar characteristics (i.e., similar amplitudes,
pulse widths, phases, peak frequencies, harmonics, etc.) in the
time- or frequency-domain prior to the noise removal step (904,
1002) in actively cleaning up the biometric pathway signal 900. In
such case, a step between 1000 and 1002 in FIG. 18 may be
configured to "normalize" the intensity of the either the
accelerometer 908 or motion pathway signal 902 based on the output
of the other.
It should be noted that FIG. 17 should not be considered a limiting
method of signal extraction for a clean PPG signal using the motion
information pathway signal 902 as a noise reference, but rather an
exemplary method. As described earlier, a variety of filtering
methodologies may be applied to clean up the biometric information
pathway signal 900 using the motion information pathway signal 902
as a noise reference. Moreover, in the embodiment shown in FIG. 17,
the subtractive filter 904 may comprise a simple subtraction
filter, an adaptive filter, a heuristic filter, or the like. As
described earlier, the filter may also comprise a redaction
approach to selectively remove signals (such as unwanted
frequencies) from the biometric information pathway signal 900
using the motion information pathway signal 902 and/or
accelerometer 908 signal as a noise reference. A redaction approach
can be especially useful for removing unwanted spectral harmonics
of motion noise from the biometric information pathway signal
900.
As described earlier, in some embodiments of FIG. 17, the
subtractive filter 904 may further comprise a spectral transform
generator such that the subtraction process proceeds in the
frequency domain. It should be noted that, in general, the filters
used to remove motion noise as described herein may be analog
and/or digital in nature, and the subtractive filter 904 may
comprise at least one digital algorithm and/or may comprise an
analog filter. A static or active analog filter may be used, but an
active analog filter may be more beneficial as it may facilitate
the active removal of time-dependent motion noise
characteristics.
It should also be noted that although heart rate extraction is
discussed at length regarding embodiments of the present invention,
the invention is not limited to heart rate monitoring. A cleaned-up
PPG sensor output may also be processed to extract other
parameters, such as RRi, breathing rate, blood pressure, SpO.sub.2,
blood hydration level, vascular compliance, heart rate variability
(HRV), blood analyte levels, mathematical operations on the
waveform (such as integrals, derivatives, transforms, and the
like), and various other blood-flow-related properties (such as
blood flow rate, volume, density, and the like), and these
parameters may be processed together (i.e., by a processor in a
wearable device) and organized in a data output such as a serial or
parallel data stream.
Referring to FIG. 18, an exemplary method of utilizing various
embodiments of the optomechanical sensors described herein, perhaps
using the system of FIG. 17, is illustrated. Optical scatter data
is alternately collected from the biometric information pathway
signal 900 and motion information pathway signal 902 by alternating
pulsing of the optical emitters associated with the respective
pathways (Block 1000). For example, the emitter(s) associated with
one pathway may be in a power-on state when emitter(s) from the
other pathway is in a power-off state.
A subtractive filter, such as subtractive filter 904, is applied to
the collected data using the motion information pathway signal 902
as a motion noise reference to generate a cleaner biometric signal
(Block 1002). Biometric parameter information is then extracted
from the biometric signal (Block 1004) and communicated to another
device or system (Block 1006). It may be beneficial to communicate
the extracted biometric parameter information as a serial string of
consecutive values representing the biometric values of each
extracted biometric parameter. Moreover, it may be beneficial for
the serial string to comprise information about the type of
biometric parameter and the confidence in the value of the
biometric parameter [see U.S. patent application No. 8,923,941,
which is incorporated herein by reference, in its entirety.
Embodiments of the present invention are not limited to "wearable"
embodiments (i.e., embodiments where a sensor module or monitoring
device is worn by a subject). Embodiments of the present invention
also may be applied in "one-touch" or acute sensing applications.
For example, FIG. 19 illustrates a biometric sensor module 2000 for
a finger or other digit F. The illustrated sensor module 2000 is an
internal optomechanical sensing module having first and second
optical emitters 14, 16, and an optical detector 18, as described
above. The illustrated sensor module 10 also includes a stabilizer
member 22 that is configured to transfer motion information from
the finger F of the subject to the optical detector 18 such that
when the digit F is pressed upon the biometric sensor module, this
motion information (such as that caused by skin displacement,
pressure changes, blood displacement, and the like), is transferred
to the stabilizer member 22, modulating the light scattered in the
motion noise pathway. The illustrated sensor module 2000 produces
two optical pathways 30, 40. The first optical pathway 30 (the
"motion information pathway") is created by light emitted by the
first optical emitter 14 and reflected off of the stabilizer member
22. The second pathway 40 (the "biometric information pathway") is
created by light emitted by the second optical emitter 16 that is
absorbed, scattered, and/or reflected by tissue, blood vessels,
etc., within the finger F of the subject. The biometric information
pathway 40 contains a higher level of subject physiological
information than the motion information pathway 30, which may
contain a higher level of subject motion information than
physiological information.
The sensor module 2000 of FIG. 20 is similar to the sensor module
2000 of FIG. 19 except that an optical barrier 20 is provided to
prevent light emitted by the emitter 14 from being exposed to the
user's skin. (Note that in FIG. 19 there may be a small gap where
light from the emitter 14 may reach the skin of the user. The
barrier 20 in FIG. 20 can prevent this.) This barrier 20 may be
critical when using the motion noise pathway signal as a noise
reference during biometric parameter extraction (FIGS. 17 and 18),
as it is important that the motion noise signal has little or no
physiological information that might inadvertently be removed from
the biometric pathway signal during the biometric parameter
extraction process.
As with other embodiments described herein, the optical detector 18
can be shared or each pathway (i.e., the biometric information
pathway and motion information pathway) may have its own detector.
Sharing the same detector has the benefit of potentially improving
the linearity (in signal amplitude and phase, for example) between
unwanted motion noise in the biometric information pathway signal
40 and motion noise detected by the motion information pathway
signal 30.
The light guiding region 52 of the biometric information pathway
and the light modulating region 50 of the motion information
pathway may each include pliable materials, such as optically
transparent silicone. The light modulating region 50 is covered
with an optically opaque or light scattering stabilizer 22 (such as
a light-scattering layer, an opaque silicone, or other opaque and
pliable material). In this way, both biometric (PPG) and motion
information may be captured by the optical detector 18. However, it
should be noted that the function of the motion information pathway
is to capture motion information, and this may be achieved with
rigid material, as well, e.g., via vibrations in a rigid solid. For
example, the light guiding/modulating regions may utilize
polycarbonate, glass, or other rigid, optically transparent
materials. Alternatively, the light guiding region 52 of the
biometric information pathway may be comprised of rigid material
and the light modulating region 50 of the motion information
pathway may be comprised of pliable material.
The stabilizer(s) may preferably be comprised of pliable material,
but it is possible to use rigid material that is sufficiently
opaque or another material that can scatter light with body motion.
Important aspects of the stabilizer are: a) it must not be
optically transparent, as light from the emitter 14 should not
reach the skin of the user, and b) it must be able to scatter light
proportional to body motion such that moving the digit F against
the stabilizer should modulate light scattered in the motion noise
pathway.
Although FIGS. 19 and 20 illustrate an internal optomechanical
sensor configuration, it should be noted that an acute sensing
embodiment may also be achieved using external optomechanical
embodiments, such as those illustrated in FIGS. 3-5, 7 as well as
the other internal optomechanical embodiments described herein.
FIGS. 21 and 22 illustrate an optomechanical sensor configuration
as it may be applied to an electronic device 2100, such as a
smartphone or other electronic device. The illustrated device 2100
includes a finger-shaped indentation 2102 that is configured to
receive a portion of a subject's finger therein. An optomechanical
sensor module 2120, such as illustrated in FIGS. 19 and 20, is
located within the finger-shaped indentation 2102. The
optomechanical sensor module 2120 may be any of the internal or
external optomechanical sensor modules described herein.
A plurality of stabilizing elements 2104 are positioned within the
finger-shaped indentation 2102 and are configured to support and
stabilize a subject's finger F at the location of the
optomechanical sensor 2120. These stabilizing elements may be like
members 222 in FIG. 9. Namely, they are not meant to transfer
motion information (unlike stabilizing members 232 and 234 in FIG.
9), but rather are used for stabilizing (supporting) the sensor at
the body.
This illustrated configuration may be particularly useful for
one-touch acute sensing of PPG-related biometrics, such as heart
rate, respiration rate, blood pressure, hydration level, metabolic
rate, cardiac output, blood analyte levels, blood oxygen levels,
hemodynamics, and the like. In some embodiments, to enhance blood
perfusion during PPG measurements, thereby increasing the
signal-to-noise of the PPG waveform information, a vibrational
motor within the smartphone 2100 may be engaged to encourage blood
flow to the outer layers of the skin of the finger F, perhaps
controlled via an algorithm as described below with respect to FIG.
23.
The various optomechanical sensor modules described herein may be
combined with a blood flow stimulator to help increase blood
perfusion in the area of the body interrogated by optical
radiation. A blood flow stimulator may be integrated within a
sensor module or an electronic device comprising a sensor module
(such as the smartphone 2100 illustrated in FIGS. 21 and 22). A
variety of blood flow stimulation methodologies may be implemented,
including, but not limited to: thermal, electrical, mechanical,
acoustical, and electromagnetic. For example, a heating element for
blood flow stimulation may comprise a resistive heating filament,
an infrared (IR) heater (also electromagnetic), or the like may be
integrated into a sensor module or an electronic device comprising
the sensor module. An electrical element for blood flow stimulation
may comprise one or more electrode pairs. A mechanical blood flow
stimulator may comprise a motor or other mechanical actuator, such
as piezoelectric actuator, acoustomechanical actuator,
thermomechanical actuator, electroactive actuator, and the
like.
In addition, the actuator used within a smartphone to generate
haptic feedback may be used to stimulate blood flow, for example,
by initiating a vibrational sequence during a PPG measurement
process. An acoustical element may comprise an acoustical generator
for generating sonic (or ultrasonic) waves that encourage blood
flow below the optical interrogation zone of the optomechanical
sensor module.
Because many smartphone and other electronic devices include
vibrational actuators, no new mechanical hardware may be necessary
for blood flow stimulation. An algorithm, such as that shown in
FIG. 23, and described below, may be applied to stimulate blood
flow, interrogate the skin with light, remove motion noise, and
generate a PPG-derived biometric.
In contrast, integrating other types of blood flow stimulators into
smartphones and other electronic device may require additional
considerations. For example, it may be important for a resistive
heating element to be in thermally conductive communication with a
skin-interface thermal conductor for coupling thermal energy
between the resistive heater and a subject's skin. Similarly, a
skin-interface electrical conductor may be important for coupling
electrical energy between the embedded electrodes and the skin.
Moreover, a thin layer of gold or conductive polymer may be
important for preventing corrosion or degradation of such
skin-interface conductors. For the case of a radiative IR heater,
an IR-transparent optical window (such as sapphire, IR-transparent
ceramics, metal fluorides, metal selenides, silicon, germanium, and
the like) may be important for coupling thermal energy between the
IR heater and the subject's skin.
Referring now to FIG. 23, a method that may be implemented in
conjunction with an optomechanical sensor module and blood flow
stimulator to improve PPG measurements, according to some
embodiments of the present invention, is illustrated. The method
may be executed by one or more processors in communication with the
sensor outputs from an optomechanical sensor module. For example,
in some embodiments, the method of FIG. 23 may be controlled by a
processor running a smartphone app.
The illustrated method may start by first determining if a
subject's skin is in sufficient proximity to a optomechanical
sensor using a proximity detection routine (Block 1100), such as
via an optical threshold detection methodology, sensor fusion, or
similar proximity detection methods. If the skin is deemed to be
sufficiently close to the sensor, then the processor(s) may
determine whether the blood flow (perfusion) beneath the user's
skin is sufficient (Block 1104), for example, using a signal
quality detection methodology. Because the optomechanical sensor is
a PPG sensor, this can be achieved by analyzing the quality of the
PPG waveform, the signal-to-noise ratio of the PPG signal, blood
oxygen level using SpO2 sensing, or the like. Examples of such PPG
signal quality methodologies are described in U.S. Provisional
Patent Application Ser. No. 62/056,510, the contents of which is
incorporated herein by reference in its entirety. Once proximity is
confirmed and perfusion is deemed by the algorithm to be
sufficient, biometric calculations may then be executed to generate
at least one PPG-based biometric (Block 1108). If the perfusion is
deemed to be insufficient (Block 1104), then a blood flow
stimulator may be engaged to stimulate blood flow and to continue
operation until the perfusion is deemed to be sufficient for at
least one biometric measurement (Block 1106). Although this example
of implementing the method of FIG. 23 is given with respect to
integration within a smartphone, the method may be executed via
virtually any sufficiently powerful processor and associated
circuitry of other electronic devices.
FIGS. 24 and 25 illustrate the combination of an optomechanical
sensor module and blood flow stimulator, according to some
embodiments of the present invention. FIG. 24 is a top view of a
device 2200, such as a smartphone or other electronic device, in
which an optomechanical sensor module 2202 is integrated. The
device includes skin interface elements 2204, 2206 which may be
electrodes, thermal conductors, acoustic generators,
electromagnetic (i.e., IR) radiators, mechanical actuators, or the
like, depending on the methodology used to stimulate perfusion
(blood flow).
FIG. 25 is a cross-sectional view of the device 2200 of FIG. 24 and
illustrates a thermally conductive blood flow stimulator (BFS) 2204
and an IR (radiative) BFS 2206. For the thermally conductive BFS,
an air-filled void or other heat conduction medium may be used to
conduct heat from the resistive heater to the skin interface
thermal conductor. For the case of the IR BFS, a vacuum, an
air-filled void, or other IR-transparent medium may be used, since
the stimulation energy is radiative and not conductive.
It should be noted that although two blood flow stimulators (2204,
2206) are shown in FIG. 25, it may not be necessary to have both in
a device. Rather, these two stimulators are shown to represent how
each might be integrated into a device. In some cases, the
optomechanical sensor module 2200 may be surrounded by an array of
blood flow stimulators of the same type (i.e., all thermal, all IR,
all acoustic, all electrical, etc.) or of a plurality of types.
FIG. 29 is a top view of a device 2200, such as a smartphone or
other electronic device, in which an optomechanical sensor module
2202 is integrated. The illustrated device 2200 includes a BFS 2204
in the form of a resistive heater having a heating element 2205 is
at the surface of the skin interface. A variety of resistive
heaters suitable for heating human skin are well known in the art.
Also shown in FIG. 29 is a piezoelectric actuator membrane 2210,
which may alternatively, or additionally, be used to stimulate
blood flow at the area of the body illuminated by the
optomechanical sensor module 2202.
Embodiments of the present invention may include micro- or
nano-fabricated devices. For example, FIGS. 26A-26D illustrate an
integrated micro-fabricated optomechanical sensor module 3000
fabricated using standard micro-manufacturing processes commonly
used to fabricate MEMS devices. FIG. 26A is a side view of the
optomechanical sensor module 3000, and FIG. 26D is a top plan view
of the optomechanical sensor module 3000. FIGS. 26A-26C illustrate
a potential fabrication sequence for generating the module 3000 of
FIGS. 26C-26D.
The illustrated optomechanical sensor module 3000 includes four
mesa LEDs 3002, two of which are utilized for the biometric signal
pathway, and two utilized for the motion (noise) pathway. In the
illustrated embodiment, the LEDs 3002 may be comprised of
AlxlnyGa1--x--yN, AlxlnyGa1--x--yAs, or other optoelectronic
materials, and the substrate 3004 may be sapphire, SiC,
AlxlnyGa1--x--yN, AlxlnyGa1--x--yAs, silicon, or other suitable
material. In the illustrated embodiment, the LED electrodes are not
shown for simplicity, but in principle a suitable layout would be
for the electrodes to extend to the periphery of the substrate
surface, protected under oxide, and exposed for wirebonding at the
periphery. Similarly, opaque barrier regions between the LEDs 3002,
which may be useful for preventing direct light contamination from
neighboring LEDs 3002, are not shown for simplicity.
The LEDs 3002 may be forward biased to emit light and
reverse-biased to detect light. Thus, if at least one LED 3002 in
each pathway is forward-biased and at least one other LED 3002 is
reverse-biased, then a suitable optical emitter-detector combo may
be achieved. Thus, a reverse-biased LED may behave as an optical
detector as described herein.
Numerous methods of generating a micro-fabricated optomechanical
module 3000, according to embodiments of the present invention may
be utilized. For example, once the LEDs 3002 are fabricated, one
method is to selectively deposit a sacrificial layer 3006 and a
support layer 3008 over the motion pathway LEDs 3002. Then, as
shown in FIG. 22B, the support layer 3008 may be etched down a few
microns followed by a selective deposition of a membrane layer
3010. An important function of the membrane layer 3010 (analogous
to the stabilizer 22 described in FIGS. 19-20) is to move with
motion and to scatter light generated by the forward-biased LED
3002 so that the reverse-biased LED 3002 may collect the motion
noise information. As shown in FIG. 22C, the sacrificial layer 3006
can then be removed to provide a membrane 3010 over the motion
pathway LEDs 3002, supported by the etched-back support layer 3008.
A variety of sacrificial layers, support layers, and membrane
layers are well known to those skilled in the art and come from a
non-limiting list of oxides, nitrides, metals, polymers, and
semimetals.
FIG. 27 illustrates a system 4000 for generating high-quality PPG
data and communicating this data to a secondary device or system,
according to some embodiments of the present invention. The
illustrated system 4000 can be integrated within a single discrete
electronic module or can be distributed throughout, or embedded
within, another electronic device (such as the smartphone 2100
shown in FIGS. 21 and 22). The dotted-line around the biometric
pathway 4006 and motion noise pathway 4008 is meant to emphasize
that these pathways are most likely to be integrated within a
discrete module 4004 as described above (e.g., sensor module 2000
of FIGS. 19-20, etc.). One specific embodiment of such a system is
illustrated in FIGS. 21-22. For example, the power circuitry 4002,
A/D circuitry 4010, blood flow stimulator and associated circuitry
4014, and communication circuitry 4012 may all be part of the
existing hardware inside a smartphone, such as smartphone 2100 of
FIGS. 21-22. The optomechanical sensor module 4004 is powered by
the smartphone circuitry and communicates information with the
smartphone circuitry.
However, in another specific embodiment, all of the functional
blocks of FIG. 27 may be integrated together in a discrete module,
such as a printed electronics circuit board (PCB) with supporting
housing, optomechanics, or the like. In some embodiments, a
secondary device or system may comprise a remote system or device,
and communication between the two systems may occur via standard
electrical or wireless protocols.
FIG. 28 depicts how embodiments of the present invention may be
integrated into an earpiece 5000. Though only one optomechanical
sensor module may be required for generating clean PPG information,
multiple optomechanical sensor modules 5002 are shown at various
locations of the earpiece 5000, representing potentially good
locations for coupling both physiological and motion information
between the ear and the module. The optomechanical sensor modules
may be either internal or external optomechanical embodiments, or
combinations of both, as described earlier. The illustrated
earpiece 5000 includes a housing 5004 surrounded, at least
partially, by a cover 5006, and a speaker driver 5008 within the
housing 5004.
The combinational stimulation-sensor system of FIGS. 24, 25, and
29, comprising a sensor module 2202 and blood flow stimulator(s)
2204, 2206, 2208, may further comprise at least one biometric
temperature sensor 2220, exposed to the skin, to collect thermal
data from the illuminated region of the body for estimating the
temperature of the skin, blood, or other tissue in proximity to the
blood flow stimulator. The biometric temperature sensor 2220 is
configured to be proximal to a blood flow stimulator (e.g., 2204,
2206, 2208) and in thermal communication with the skin of the user.
Such a sensor 2220 may comprise a biometric temperature sensing
element coupled to a skin interface thermal conductor. As a
specific example, such a sensor may comprise a io
temperature-sensing IC (integrated circuit) coupled to an exposed
metallic contact (the skin interface thermal conductor), such that
the exposed metal contact, when in contact with the skin of the
user, transfers thermal energy to the sensing element for
generating an electrical signal comprising skin temperature
information. Numerous wearable skin temperature sensing
configurations are well known to those skilled in the art, and
various types of thermal sensing elements--an IC, thermistor,
thermocouple, IR sensor, RTD (resistance temperature detector), or
the like--may be employed along with various thermal
conductors.
In the illustrated system 4000 of FIG. 27, the blood flow
stimulator 4014 comprises a thermal generator and biometric
temperature sensor 4016 worn proximal to the skin, as described
above. The system 4000 may be employed towards
temperature-dependent sensing of blood and tissue (i.e., skin,
muscle, etc.) which is interrogated by both light from optical
emitter(s) of the sensor module 4000 (e.g., sensor module 2202 of
FIGS. 24, 25, 29) and thermal energy from skin interface element(s)
of one or more blood flow stimulators 4014. In combination with a
processor, the system 4000 can be used to actively control
stimulation as well as to actively characterize biometric
information from the blood or tissue.
The thermal information collected by the biometric temperature
sensor 4016 may be processed by a processor to: 1) estimate the
temperature of the skin, blood, or tissue that is being illuminated
by the optical emitter of a PPG sensor module, and 2) gauge the
thermal dosage applied to the skin by the blood flow stimulator
4014, providing feedback for active control of the thermal energy
dosage. For example, an algorithm executed by the processor may
process the thermal energy information to determine if the dosage
is higher or lower than a determined threshold. In such case, the
processor may then communicate information to the controlling
electronics that the intensity of the blood flow stimulation is to
be reduced or increased accordingly. Such a configuration may help
prevent burning of the skin while assuring that enough thermal
energy is supplied to generate sufficient blood perfusion in the
illuminated body region.
Additionally, a stimulation-sensor system+biometric temperature
sensor, according to embodiments of the present invention, may also
be applied towards temperature-dependent biometric
characterization. For example, with supporting analog and/or
digital control electronics/circuitry, light generated by an
optomechanical sensor module (e.g., sensor module 2202 of FIGS. 24,
25, 29) may be time-synchronized with a thermal blood flow
stimulator to execute temperature-dependent biometric analysis of
the blood, skin, or tissue via temperature-dependent optical
absorption, scattering, polarization, and/or luminescence. Namely,
since the interaction between light and biological materials may
change with changes in temperature, analyzing the PPG signal from
the system 4000 during multiple skin, blood, or tissue temperatures
can be used to identify the presence and concentration of skin,
blood, and tissue constituents.
As a specific example, the intensity vs. optical wavelength
characteristics of biological luminescence of a body region,
typically induced by illuminating the body region with optical
wavelengths between 200 nm and 490 nm, is known to depend on the
temperature of the body region, and this temperature dependence may
be different for differing luminescent species. Thus, by
controlling the localized body temperature over set ranges and
recording luminescence intensity over those set temperature
ranges--or even more so by recording optical excitation
wavelength-dependent luminescence intensity over those temperature
ranges--and then analyzing these wavelength-dependent luminescence
intensities in context of biological luminescence models,
constituents of the localized excitation region may be
characterized.
Referring to FIG. 30, in one embodiment, the system 4000 of FIG.
27, for example, may be applied towards generating physiological
assessments by: 1) first determining if the blood perfusion level
is acceptable for measurement (Block 6000), such as via the method
described above with respect to FIG. 23, 2) taking measurements of
both biometric optical sensor data and biometric temperature sensor
data (Block 6002), 3) analyzing the optical sensor data in context
of the temperature sensor information (Block 6004), and 4)
generating a physiological assessment based on the analysis of this
data (Block 6006). This method is particularly well-suited for
collecting PPG optical scatter data with changes in the temperature
of an illuminated region. Key functional benefits of this
methodology include: 1) power savings may be achieved by executing
PPG analysis only when the subject's perfusion status is
acceptable, and 2) reducing PPG analysis errors (such as PPG-based
blood pressure measurement errors, for example) by collecting PPG
data only when the subject's perfusion status is acceptable.
In another embodiment, the temperature control of the body region
of interest (the skin and associated blood vessels, blood, etc.)
may be more deliberate once viable perfusion status is determined,
as shown in FIG. 31. In the method illustrated in FIG. 31, the
blood flow stimulator--in this case a thermal energy generator--is
turned on and off for certain periods of time; during these periods
of time, sensor readings are collected and stored (in memory) from
both the biometric optical and temperature sensors (Blocks 6010,
6012). If the PPG sensor module (comprising the optical emitter(s)
and detector(s)) is configured to generate light at multiple
wavelengths, optical sensor data at each wavelength may be stored
for each on/off cycle of thermal energy generation. This may be
achieved by cycling through each individual wavelength in time at a
set duty cycle or by utilizing an optical detector configured to
selectively detect light over a plurality of individual wavelength
ranges, as described in U.S. Pat. Nos. 8,251,903 and 8,700,111, the
contents of which are incorporated herein by reference in their
entireties. The PPG and temperature sensor data is analyzed for
"on" and "off" periods of the blood flow stimulator (e.g., a
thermal energy generator) to generate a physiological assessment
(Block 6014).
As an example of a type of physiological assessment, hemodynamic
assessments may be generated by processing the PPG data from both
"on" and "off" cycles of the blood flow stimulator (thermal energy
generator). As a specific example, the intensity of PPG peaks
(i.e., the amplitude of the PPG waveform of one or more blood flow
pulses) may be compared for both "on" and "off" cycles, and the
ratio of the amplitude of PPG intensity during "on" cycles vs.
"off" cycles can be used to assess how sensitive a subject's blood
flow dynamics may with respect to ambient temperature or various
forms of body temperature.
According to another embodiment of the present invention
illustrated in FIG. 32, thermal energy generator intensity of a
blood flow stimulator may be adjusted to various settings such that
a matrix of optical sensor signal intensities over a range of
temperatures (and over a range of optical wavelengths if
multiwavelength emitters are employed) may be generated. This
matrix may then be used to generate physiological assessments based
on a io biological model.
For example, according to the method illustrated in FIG. 32, a
blood flow stimulator (e.g., a thermal energy generator) is turned
on and thermal intensity is adjusted to a controlled setting (Block
6020). Skin temperature is determined by sensing thermal
information from the skin using the temperature sensor, and
collecting PPG data from the skin with a peak optical emitter
intensity centered at .lamda..sub.1 (Block 6022). The steps of
Blocks 6020 and 6022 are repeated over a controlled range of
thermal intensity settings to create a dataset containing PPG
related information versus temperature (Block 6024). The steps of
Blocks 6020, 6022 and 6024 are then repeated for each desired
wavelength (.lamda..sub.n) over a range from n=1 to n=k (Block
6026). The temperature vs. PPG amplitude vs. .lamda. matrix is then
analyzed to generate a physiological assessment for the subject
(Block 6028).
An example of how the method of FIG. 32 may be applied is presented
in FIG. 33, showing a plot of optical scatter (PPG) signal
intensity & bioluminescence signal intensity vs. measured skin
temperature for multiple optical excitation wavelengths
(.lamda..sub.1, .lamda..sub.2, .lamda..sub.3, .lamda..sub.n). Two
exemplary temperatures, Temp.sub.1 and Temp.sub.n, are presented on
the plot, showing how a matrix of optical
intensity--optical(Temp.sub.n.lamda..sub.n)--may be generated, such
that this matrix may be applied towards generating a physiological
assessment based on a biological model. Although the collected
optical energy detected by an optical sensor may comprise optical
scatter or optical luminescence information from multiple blood,
skin, or tissue constituents, having optical sensor data from
multiple optical wavelengths at multiple temperatures helps provide
enough data to characterize "n" constituents with "n" unknowns, as
with multi-wavelength pulse oximetry.
For the case where luminescent blood, skin, or tissue constituents
are of interest, the method illustrated in FIG. 34 may be employed
to generate a matrix of temperature-dependent optical intensities
over time--optical(Temp.sub.n.lamda..sub.nt.sub.n)--over an optical
scattering time period t.sub.scatt and an optical luminescence
period t.sub.lum. For example, as illustrated in FIG. 34, a blood
flow stimulator (e.g., a thermal energy generator) is turned on and
an optical emitter of a PPG sensor module is turned on (Block
6030). A determination is made if skin temperature has reached a
first threshold value and remains stable at that value and, if so,
then PPG data is collected from skin at this first threshold value
starting at t=0 of a time period t.sub.on (Block 6032). This
measurement can be repeated for multiple excitation wavelengths. At
time t=t.sub.s, the blood flow stimulator (e.g., a thermal energy
generator) is turned off and time-correlated skin temperature data
and PPG data is collected over the time period t.sub.off (Block
6034). This measurement may be repeated for multiple excitation
wavelengths. The PPG and temperature sensor data is analyzed over
the time periods t.sub.on and t.sub.off to generate at least one
physiological assessment for the subject (Block 6036).
It should be noted that although the .lamda. value in FIG. 34
represents the peak optical excitation
wavelength--.lamda..sub.excit--the optical luminescence collected
may be at multiple luminescence wavelengths--.lamda..sub.lum--for a
given .lamda..sub.excit if a multiwavelength optical detector is
utilized in the PPG sensor module, as described above. An advantage
of the method of FIG. 34 is that data may be collected for both PPG
optical scatter and bioluminescence, and the characteristic
temperature dependence of both optical properties may be collected
and analyzed to generate physiological assessments.
The foregoing is illustrative of the present invention and is not
to be construed as limiting thereof. Although a few exemplary
embodiments of this invention have been described, those skilled in
the art will readily appreciate that many modifications are
possible in the exemplary embodiments without materially departing
from the teachings and advantages of this invention. Accordingly,
all such modifications are intended to be included within the scope
of this invention as defined in the claims. The invention is
defined by the following claims, with equivalents of the claims to
be included therein.
* * * * *